Two months into his presidency, Joe Biden confronted a political crisis: The number of migrants illegally crossing the southern border into the United States was soaring. So he asked Vice President Kamala Harris to lead the administration’s diplomatic efforts to reduce problems at the border.

That assignment included working with three Central American countries — El Salvador, Guatemala and Honduras — to improve living conditions and lower the odds that migrants would leave those countries for reasons including poverty, gang violence and corruption.

But Republicans quickly seized on the apparent diplomatic opportunity for Harris, referring to her as the country’s “border czar” responsible for all issues related to the U.S.-Mexico line. Now, more than three years later, her role is a potential political liability as she runs for president as the Democratic nominee and polls show voters broadly disapprove of the Biden administration’s handling of the border.

Harris, in fact, has never been in charge of the border. The Department of Homeland Security manages migration. Her immigration role for the Biden administration has included boosting U.S. aid to Central America, traveling to the region and discouraging potential migrants from making the dangerous journey to the United States.

Migration from the three Central American countries during the Biden administration has fallen 35 percent, from about 683,890 to 447,270 in 2023, lower than it was in 2019 under Trump. But analysts say it is difficult to tie the reduction in numbers to Harris’s efforts, and there have been increases in migration from other countries.

Since launching her presidential campaign, Harris has cast herself as a former prosecutor who took on undocumented gang members, a former border state attorney general in California who prosecuted human traffickers and a would-be president eager to sign into the law the toughest border restrictions in a generation.

Harris told a roaring crowd at a campaign event in Glendale, Ariz., last week that she’d put her record against Republican nominee and former president Donald Trump’s “every day of the week.”

“Donald Trump does not want to fix this problem,” she said. “He talks a big game about border security, but he does not walk the walk.”

Perhaps the most glaring example of the challenges the Biden administration has faced was in December, when nearly 250,000 migrants were apprehended, an all-time high. The numbers went down dramatically this year, largely due to increased enforcement in Mexico, where military patrols and highway checkpoints are intercepting would-be crossers at the U.S. government’s request.

Republicans initially tried to blame Harris for the influx along with Biden, but they intensified their efforts toward her after the president ended his campaign on July 21 amid concerns about his age and Harris declared her candidacy to succeed him.

Biden faced widespread voter disapproval of his handling of the border. A YouGov poll conducted for the Economist this month found that about 60 percent of registered voters disapproved of Biden’s handling of immigration, with 35 percent approving.

The day after Biden dropped out of the race, House Republicans filed a resolution that “strongly condemns the Biden Administration and its Border Czar, Kamala Harris’s, failure to secure the United States border.” A week later, Trump’s campaign released its first advertisement against Harris, assailing her over border security.

“She’s the architect of the border invasion trying to pretend she’s strong on border security,” Trump said at a rally last month in which he repeatedly blamed her for allowing millions of migrants into the country.

Democrats are rebutting GOP attacks more strongly, blaming Trump and his allies for the failure this year of a bipartisan bill that would have invested billions of dollars in border security. After that failed, the Biden administration imposed new asylum restrictions and continued working with Mexico to ramp up enforcement. Apprehensions declined to 56,400 in July, the lowest of any month since September 2020, according to U.S. Customs and Border Protection.

“They’re implementing immigration policy with one hand tied behind their back. Congress has not been helpful at all,” said Kevin Appleby, a senior fellow for policy at the Center for Migration Studies of New York, a think tank. “This is basically the administration doing this all on their own.”

Harris might not deserve personal credit for the drop in border crossings, he said, but she is part of the administration that achieved it. “You can’t blame her for certain administration policies but not give her credit for those that have been successful,” he said.

Biden and Harris had campaigned in 2020 to treat migrants more humanely after years of controversial crackdowns by Trump, whose officials made longtime immigrants targets for deportation and forcibly separated migrant parents and children at the border. The Biden team pledged to pause deportations, process asylum claims and welcome immigrants.

Harris, the daughter of immigrants from Jamaica and India, had a similar platform as a presidential candidate before becoming Biden’s running mate.

She promised to close private immigration detention centers, limit deportations and fight for a path to citizenship for the 11 million undocumented immigrants in the United States.

Those liberal approaches faced swift backlash as migration soared after Biden took office. Analysts say the Biden administration was slow to respond to triggers of mass migration, including pandemic-shredded economies, a robust U.S. job market and the perception that Biden would be more lenient than Trump.

Biden warned before taking office that he did not want 2 million people on the border, and he kept in place a Trump policy that allowed border agents to rapidly expel migrants until May 2023. But Biden also relaxed enforcement, and just as he feared, apprehensions soared to an average of 2 million a year, the highest ever recorded.

Record numbers of unaccompanied children from Central America arrived at the border, some taking dangerous jobs meant for adults. Texas’s Republican governor began busing thousands of migrants from the border to New York, Chicago and other Democrat-led cities, overwhelming their shelters and straining their budgets.

In February 2021, Biden issued an executive order pledging to address the root causes driving migration from northern Central America, which then accounted for about half of border apprehensions. The next month he asked Harris to lead the effort, noting that he had played a similar role as vice president to former president Barack Obama.

Republicans pounced, identifying Harris with rising illegal crossings and calling on the vice president to visit the border.

Harris’s allies recognized the issue as politically fraught, one that could hinder her eventual campaign to succeed Biden. U.S. presidents have struggled for decades to address immigration, with little help from an increasingly polarized Congress. Harris quickly carved out a more limited role, one that focused on the Central American countries and not on the southern border.

In June 2021, Harris made her first and only trip to the border, a 4½-hour visit touring operations in El Paso, hundreds of miles away from the busiest spot on the border. Earlier that month she also visited Mexico and Guatemala, a country Biden went to in 2014.

Like Biden, Harris urged would-be migrants in Guatemala to stay home and warned them that they could be deported.

“Do not come,” she said then. “You will be turned back.”

Her words stunned advocates for immigrants, but some in the Biden administration were increasingly alarmed about the border.

The rising numbers were a sign that Obama-era efforts to address root causes had not taken hold and were not so easy to solve in an election cycle. When Biden visited Guatemala in June 2014, Border Patrol apprehensions that month totaled 57,860. When Harris visited in the same month seven years later, apprehensions were 178,650.

The Trump administration interrupted Obama-era diplomacy to prevent migration, analysts say. Trump slashed aid to Central America, decimated refugee programs and denigrated other countries.

“We were left with a mess,” said Katie Tobin, a former Biden immigration adviser.

Advocates for immigrants said that Trump’s approach did not stop mass migration either. In 2019, attempted border crossings surpassed 850,000. The pandemic interrupted that trend in 2020 by stalling global travel and enabling Trump to expel migrants without a hearing, cutting attempted crossings in half.

It remains unclear if Trump could replicate that strategy, if elected, since the U.S. economy also rebounded more strongly than that of other countries, creating a powerful jobs magnet.

Harris focused mainly on private and public investment in Central America.

Her effort included dispatching coronavirus vaccines there, creating anti-smuggling task forces and investing $4 billion in U.S. aid to the region, but she faced challenges because Central America was riven by gangs and corrupt leaders after years of failed U.S. intervention.

“She didn’t exactly have the easiest partners,” said Roberta Jacobson, former U.S. ambassador to Mexico who served as the top White House official on the border during the early months of Biden’s administration.

Aides say Harris’s most powerful influence was in the private sector, helping to create jobs so that people would stay home.

In May 2021, she issued a “call to action” to tackle the root causes of migration from northern Central America. She met with a dozen CEOs at the White House to encourage investment in the region to create jobs and improve supply chains by moving overseas operations closer to the United States. They began with $750 million in investments, loans, housing and other resources.

Since then, more than 50 companies have gotten involved, and total investment has surpassed $5.2 billion and created more than 70,000 jobs in the region, said Jonathan Fantini-Porter, the CEO of the Partnership for Central America, the nonprofit that oversees the implementation of the effort.

Columbia Sportswear, Nespresso and auto-parts manufacturer Yazaki North America Inc., and others created thousands of manufacturing and farming jobs in the region.

Ariel Ruiz Soto, senior policy analyst at the Migration Policy Institute, said the reasons for the decline in Central America vary by country. Gang crackdowns in El Salvador, a new leader in Honduras, and increased enforcement in Guatemala and Mexico may have played a role.

“There is no direct correlation to say that the root causes strategy has led to this decrease,” Ruiz Soto said. “The reality is there hasn’t been a steady evaluation over time of these executive policies.”

“This would not be a root causes thing. There is no way that in two years it makes a difference,” said Mark Krikorian, executive director of the Center for Immigration Studies, a think tank that supports reduced immigration levels.

More likely is the intense enforcement in Mexico and increased removals from the United States are having an effect, analysts say.

Another challenge for Harris is that northern Central Americans are no longer the biggest group arriving at the border. They accounted for 71 percent of all border crossers in 2019, but so far this year are 23 percent since the number of people from China, Venezuela and other nontraditional nations has increased.

Harris has said that she would continue the Biden administration’s hard line approach to the border if she wins the presidency. She supported the bipartisan border security bill Biden backed this year, which included measures that would have effectively shut down the border if illegal crossings surpassed 5,000 a day. She has pledged to sign the bill as president.

Harris’s campaign leaned into the border messaging with a recent television ad that highlighted her support for the “toughest border control bill in decades” and her history prosecuting drug smugglers.

“As president, she will hire thousands more border agents and crack down on fentanyl and human trafficking,” the narrator said in the ad. “Fixing the border is tough. So is Kamala Harris.”

The San Francisco district attorney needed support from key unions and different parts of California when she launched her first statewide campaign.

So almost 15 years ago, Kamala Harris connected with another rising star, Laphonza Butler, then the Los Angeles-based leader of the fast-growing home-care workers union. Harris wanted the local union’s backing in her bid for state attorney general.

“First, you need to walk a day in the shoes of one of our members,” Butler, now a Democratic senator from California, recalled instructing the future vice president.

Harris took her up on it. She spent an entire day with a home-care provider in Oakland, working with the elderly and disabled in their homes. She earned the endorsement of the SEIU 2015, and went on to narrowly win the 2010 election. She also forged a long-lasting bond with Butler.

Butler has known the vice president since that first campaign and supported her next two statewide campaigns, including the Senate bid in 2016 that put Harris on the national radar. She also worked as a top policy adviser on Harris’s short-lived presidential primary campaign in 2019.

Now, through a mix of happenstance and insider smarts, Butler, 45, is poised to potentially wield far more clout than Washington expected when she was sworn in last October for an interim appointment to replace the late Sen. Dianne Feinstein (D-Calif.).

Butler has impressed colleagues who appreciate her expertise in the labor movement as well as her time running Emily’s List, the political organization charged with electing female candidates who support abortion rights. She has honed what she calls the “skill of influence” in the Senate, learning what makes all 100 tick in a chamber that would be critical to a first-term agenda should Harris win in November.

Other senators, particularly Alex Padilla (D-Calif.) and Patty Murray (D-Wash.), have close ties to Harris, but they are charting long-term careers in the Senate. Not Butler, whose tenure ends whenever California officials declare a winner in the November special election.

Friends see Butler not just as a smart temporary colleague, but possibly as a long-term power broker in a potential Harris administration with the new bonds forged during her brief time in the Senate.

“You know, she’s got executive capacity, as well as legislative skills and extraordinary personal skills. So I can see her playing a very prominent role in a Harris administration. She has enormous goodwill here,” Sen. Peter Welch (D-Vt.) said.

For now, Butler is focused on two jobs: “Senate-ing” (her phrase for her unexpected stint representing 40 million Californians), and helping Harris’s latest campaign.

“I am doing everything that I can to protect the future of this country, by helping Vice President Harris become President Harris,” Butler said in a telephone interview Wednesday.

If that works out, Butler wants to play whatever role the new president would consider.

“I believe in her and her leadership, and if she felt like there was something that I could offer, I of course would have to consider it,” Butler said. “You don’t get asked to do something by the president of the United States very often.”

In a Senate still so antiquated that some newcomers do not deliver speeches their first year in office, many interim senators in recent years have left little to show for their brief tenure.

George Helmy, the new appointee to replace Sen. Bob Menendez (D-N.J.), convicted on felony charges last month in a bribery case, is not expected to do much beyond voting the party line in the less than five months he will serve.

Some might have initially seen that role for Butler, but she quickly impressed many senators. Then the June 27 debate took place, sending President Joe Biden into a political free fall within the Democratic Party.

Butler so happened to be on a three-day trip through California with Harris at that time. When she returned to Washington the next week, she delivered the Biden-Harris mantra.

“The future of our democracy is at stake. And we’ve got to get out, do the work, not take a single voter for granted,” Butler told reporters on July 2, never wavering in her support for Biden.

Now, with Harris atop the ticket, Butler’s thoughts matter even more.

When political firestorms arise — like former president Donald Trump’s appearance on July 31 before Black journalists when he questioned whether Harris was truly Black — Butler can channel Harris’s instincts in how to respond.

“Look, this is the only tool he has. He has no vision for the country,” Butler told reporters soon after Trump’s remarks.

She provided the road map for Team Harris: Punch back at Trump’s extreme remarks, then return to pocketbook issues that the swing voters consider most important and highlight the controversial ideas of Project 2025, a far-right agenda promoted by former Trump administration officials.

“We are not going to ignore it,” Butler said then of the incendiary remarks. “But we have to actually get to a place where we’re engaged on the issues that American people care about.”

Butler grew up in Magnolia, a small majority-Black town with a population of just a few thousand, 85 miles south of Mississippi’s state capital, where she attended Jackson State University. After several union-organizing jobs for nurses and janitors in places like Baltimore and Philadelphia, Butler moved to Los Angeles to run the home-care workers union.

California Gov. Gavin Newsom (D) appointed Butler to the Senate in October after Feinstein’s death, following a series of prolonged health battles. In early 2021, Newsom promised to appoint a Black woman to replace Feinstein if she ever could not finish her term, after he had just appointed Padilla, the first Latino senator from California, to replace Harris in the Senate.

By summer 2023, Feinstein had already announced she would retire and there was a full-scale campaign launched among several competitors. Newsom did not want to interrupt that race by choosing sides, leading many to think he would appoint someone who promised to serve briefly and not run a full term.

That angered some Black activists who felt it was patronizing to appoint a Black woman to serve in the job only temporarily.

When he chose Butler, Newsom won plaudits from liberal activists across California and he also gave her carte blanche to run for the seat if she wanted it.

Despite the head start that the eventual Democratic nominee, Rep. Adam Schiff, and others had, Butler analyzed the race as if she were a hardheaded political strategist again.

“Could I raise the money? Could I get the endorsements? Would I actually be able to take some endorsements from folks who were already in the race? And the answer to those questions was, yes, and absolutely,” she said.

And she talked to Harris. “Never did she tell me what to do. She doesn’t — she’s not that kind of a mentor and a friend. She is the kind of friend who talks through all of the different aspects and opportunities, the challenges, the sacrifices, the pluses and minuses,” Butler said.

Instead, with a young daughter who would be 16 at the end of a full six-year term, she and her wife decided it wasn’t the right time for elective politics.

And now, after one crazy month of July, she gets to focus again on helping Harris in the campaign of her life.

Butler has been impressed with Harris’s ability to take the already existing Biden-Harris campaign and scale it up to include several prominent veterans of previously successful presidential campaigns, something that was lacking in Harris’s bid five years ago.

“While you have people who are strategists and/or other kinds of experts, the experience of running a presidential campaign is invaluable,” she said.

Still more of an executive than a legislator, Butler has relished having a front-row seat for major legislative battles, including the border crisis and funding Ukraine’s defenses. She became a fully engaged senator without having to grind through raising tens of millions of dollars to try to win an election.

Welch, 77, reached the Senate nine months before Butler did, and only after a lengthy career that started in state politics in 1981. Despite three decades in age difference, they find themselves in a similarly junior status and often remain studiously quiet during caucus lunches.

They then find ways to buttonhole key senators to try to privately influence debates, Welch said. “She combines the capacity to be very direct and clear with an open and welcoming demeanor. She’s gifted.”

Any question about the next job, however, prompts Butler to focus on the more important job directly in front of her.

“I am resolute, in my demonstration of my commitment to the future where my daughter can believe that she can one day be president,” she said. “And I think this is our opportunity to do that.”

One month ago, Democrats watched with envy and dismay as Republicans demonstrated their energy and unity with a lively party convention that showcased Donald Trump’s dominant position in the race against President Joe Biden.

Now, after one of the most momentous shifts in political atmospherics in modern history, Democrats have been buoyed by a new standard-bearer and sense of optimism as they prepare to begin their own nominating convention Monday in Chicago.

Biden will speak on the first day of the convention before leaving town, a symbolic changing of the guard that highlights how his decision to abruptly end his reelection bid upended the race.

Vice President Kamala Harris, who has ridden a wave of enthusiasm in a party that had been riven by angst over Biden’s weak poll numbers, will cap the programming Thursday with a speech designed to introduce herself to the nation and highlight the historic nature of her unexpected candidacy. The unprecedented turn of events has added to the sense of unpredictability that has marked an election already rocked by a history-changing debate, one candidate’s felony convictions and an assassination attempt during a political rally.

“It is remarkable,” said Julian Zelizer, a presidential historian at Princeton University. “An incredibly important election, which made the Democratic convention interesting from the start, is now truly distinct. The entire ticket has changed, the energy is different, and what the party is putting forth as the faces of the party has transformed the terms of the competition.”

While much about the convention has changed in recent weeks, the party gathering will no doubt feature a steady dose of criticism of Republican nominee Trump, who has seen his campaign upended since he rose from the ground and shouted “fight, fight, fight!” after surviving an assassination attempt last month. In recent days, he has been flailing in public as polls show him ceding his advantage in the race to Harris.

Democrats hope to use the four-day convention to build on their momentum, balancing their attacks on Trump with a push to boost Harris and her running mate, Minnesota Gov. Tim Walz (D), in the minds of millions of voters who remain undecided.

But even as Democrats plan to celebrate their sense of unity around Harris’s ascension, the area outside the convention hall will showcase some persistent divisions.

Protesters have promised to bring tens of thousands of people to Chicago to denounce the war in Gaza and the Biden administration’s support for Israel — plans that began while Biden was still running and have continued even as Harris has tried to offer a more empathetic tone about the plight of Palestinians.

Harris’s aides plan to use the convention both to introduce her to the public and to draw a contrast with Trump, said Michael Tyler, communications director for the campaign.

The event will feature top Democratic leaders, including former presidents Barack Obama and Bill Clinton, and former secretary of state Hillary Clinton, the party’s 2016 nominee. Several major celebrities are expected to attend, a sign that Harris may be able to create the kind of cultural movement that eluded Biden.

And even as party leaders plan to celebrate their improved political standing under Harris, officials hope to deliver the message that the contest against Trump remains close.

“You look at the state of polling, and obviously, things look good right now, but this remains a margin-of-error race,” Tyler said. “And we know that it’s going to come down to tens of thousands of votes in a handful of states.”

The made-for-television convention stands as the highest-profile moment thus far in Harris’s truncated campaign for the presidency. In a typical presidential race, a candidate’s most significant moments include the day they launch their campaign, the day they secure the nomination and the day they announce a running mate.

Usually, those moments are spread out over many months. For Harris, they all happened within three weeks.

Trump remarked on the rapidly changed race during a news conference Thursday, criticizing Harris while noting how much her fortunes have improved.

“Six weeks ago, she was considered to be a failed vice president in a failed administration — a disaster,” Trump told reporters. “Now, all these people are talking about her like she’s Margaret Thatcher, liberal version.”

At times, Trump has struggled to focus on policy criticisms of Harris, instead attacking her race, gender or intelligence. His campaign has sought to press his advantage on the economy in recent days, staging events ostensibly designed to criticize Harris over inflation and economic instability.

The former president plans to continue that approach during a speech on the economy Monday in York, Pa., offering some counterprogramming as the Democrats’ convention kicks off.

“Kamala Harris says inflation will be a ‘Day One’ priority, but her ‘Day One’ was three and a half years ago,” Trump’s campaign said in a statement announcing his speech. “The Harris-Biden Administration created inflation, putting Kamala in charge won’t do anything different to fix it.”

The Trump campaign’s focus on inflation comes at an awkward time: The headline inflation number dropped to its lowest level in three years last month, and unemployment has remained relatively low for most of Biden’s term, facts Democrats have been highlighting ahead of their convention.

In recent days, Harris has begun outlining some of her policy proposals, including a $25,000 subsidy for first-time home buyers, a ban on price gouging on groceries and a child tax credit that would provide $6,000 per child in the first year of a baby’s life. The convention — where parties traditionally lay out their platform — will offer a high-profile opportunity for her to explain how her presidency would differ from Biden’s and what she hopes to accomplish if elected. Before her acceptance speech on Thursday, Harris is planning to launch a bus tour in Pennsylvania on Sunday and hold a rally in Milwaukee on Tuesday.

In Chicago, Harris will face the delicate task of celebrating Biden’s accomplishments while trying to distance herself from the low marks he has received from voters on inflation, immigration and other top issues.

Republicans have sought to tie Harris to Biden and paint her as an even more liberal candidate, often pointing to the positions she embraced during her unsuccessful presidential campaign five years ago. Harris has since disavowed many of those positions, including support for Medicare-for-all, a ban on fracking and mandatory buybacks for assault rifles.

Speaking in North Carolina on Friday, Harris tried to lay out her own vision for improving the economy, proposing programs to eliminate medical debt and cap prices for prescription drugs.

“We know that many Americans don’t yet feel that progress in their daily lives,” she said, after touting the economic gains made since Biden took office. “Costs are still too high and on a deeper level for too many people, no matter how much they work, it feels so hard to just be able to get ahead.”

That sentiment — which formed the theme of much of the Republican convention last month — was one reason polls showed Biden trailing Trump for much of the past year. Biden’s stumbling debate performance on June 27 — an unusually early date that was intended to help improve his standing against Trump — reignited Democratic fears that the president was on track to lose the race. Post-debate polls showing Biden falling further behind Trump both nationally and in swing states led top Democrats to urge the president to step aside.

Biden’s decision to drop out of the race and endorse Harris has created the first major shift in the race toward Democrats, with polls showing the vice president now leading Trump nationally and in several swing states.

Biden’s exit from the race also changed the nature of the convention Democrats were planning. Aides have spent the past few weeks creating programming and advertising around the biography and vision of Harris, replacing what was once designed as a celebration of Biden’s journey from Scranton, Pa., to the White House.

But Democratic attacks on Trump are unlikely to change much.

“The fact of the matter here is that our opponent remains the same in Donald Trump,” Tyler said. “The threat remains the same in Donald Trump. The extremism that he wants to enact on the American people remains the same.”