The region is riddled with corrupt government officials, the drivers of migration are deeply rooted in economic inequality and social factors - and she didn't control the border.
"She was given a very hard, difficult, convoluted portfolio," said U.S. Senator Chris Murphy, a Democrat on the Foreign Relations Committee and an architect of a bipartisan border security bill introduced earlier this year.
At campaign rallies and in social media posts, Republican presidential candidate Donald Trump has intensified his attacks on Harris as a failed "border czar," especially now that she has emerged as the likely Democratic nominee after President Joe Biden ended his campaign for reelection this month.
Despite Harris' efforts, some 7 million migrants have been arrested illegally crossing the U.S.-Mexico border under Biden, according to government data, all-time highs that have fueled Republican criticism.
The reality of Harris's record on migration is far more complicated, according to interviews with three current Biden officials, 13 former officials and others tracking the issue.
First, Harris was never given the portfolio of border czar, said Alan Bersin, who embraced the label as a special representative for border affairs under Presidents Barack Obama and Bill Clinton. "This was not the job assigned to VP Harris," he said.
Instead, Biden asked Harris to lead diplomatic efforts to reduce poverty, violence and corruption in Central America's Northern Triangle countries of Guatemala, Honduras and El Salvador, as well as engage with Mexico on the issue.
It was similar to the job Biden had when he was vice president.
But that was an overly broad mission, Murphy said.
"It's hard in a short period of time to come up with a strategy that impacts the very real and complicated psychological decision-making that people in those countries go through when they're deciding to come to the United States," Murphy said in a phone interview.
And within months of Harris taking the job, the focus on the three Central American countries was out of step with the reality at the border - where illegal immigration from Cuba, Haiti, Nicaragua and Venezuela was spiking, several former officials and outside experts said.
"She started off, in a sense, at a disadvantage because everyone was focusing on those three countries in the Northern Triangle," said Roberta Jacobson, who served as a coordinator for the U.S.-Mexico border in the early months of the Biden administration. "Meanwhile, the migrant population was changing dramatically."
Harris continued to lead the Central America effort although she has increasingly focused on abortion rights this year, a top Democratic issue since a 2022 U.S. Supreme Court decision struck down the nationwide right to an abortion.
The White House said in March that Harris helped engineer $4 billion in government aid and commitments of $5.2 billion in private investment to create or support an estimated 250,000 jobs in Guatemala, Honduras and El Salvador.
Nespresso started sourcing coffee from El Salvador and Honduras in 2021. Gap Inc said it is on pace to meet a pledge to invest $150 million by 2025 to source textiles in the region and that it had increased yarn production in Guatemala and provided skills training to women in Guatemala and Honduras.
Ricardo Barrientos, director of the Central American Institute of Fiscal Studies think tank, said the U.S. aid and private sector investment was a fraction of the remittances migrants from the three countries working in the U.S. send home each year – $37 billion last year alone.
"It's very small compared to the magnitude of the challenge," he said. "Or some would say, 'too little, too late.'"
By May, the number of migrants from the Northern Triangle caught crossing illegally had fallen to 25,000 from a peak of 90,000 in July 2021 - although experts say the impact of Harris' efforts remain unclear.
'BORDER CZAR'
Harris made two trips to Central America: Guatemala in June 2021 and Honduras in January 2022. That was one fewer than Biden, who made three trips to Guatemala after he was assigned a similar role in 2014.
Meanwhile, Republicans began identifying Harris with rising illegal crossings and called on her to visit the border. She made her first and only visit to U.S. border operations in El Paso, Texas, in June 2021, where she defended her portfolio.
"The reality of it is that we have to deal with causes, and we have to deal with the effects," she told reporters at the airport.
During the six-hour visit, Harris toured a migrant processing center, speaking with a group of girls, her office said at the time. But she did not tour the border wall on foot, according to pool reports, which Trump officials did routinely.
Raul Ortiz, the Border Patrol chief from 2021-2023, said he never spoke with Biden or Harris although he met with Trump and then Vice President Mike Pence more than once despite holding a lower rank during that administration.
"I would have liked to have had an opportunity to discuss some of the issues and some of the recommended changes that I thought we should have implemented," Ortiz said.
The White House said in March that Ortiz had been invited to join Biden in El Paso last year and did not attend, although Ortiz contested that, saying he was not invited.
LIABILITY OR ASSET
Immigration is the third-highest concern of U.S. voters behind the economy and extremism, according to a Reuters/Ipsos poll in June, and voters favored Trump's approach to immigration over Biden's 44%-31%.
A Trump campaign attack ad aired in six election battleground states on Tuesday showed images of migrants attempting to illegally cross the border, tying the issue to crime and pinning the blame on Harris.
Studies show immigrants do not commit crimes at a higher rate than native-born Americans.
"If border czar Harris stays in charge, every week will bring a never-ending stream of illegal alien rapists, bloodthirsty killers and child predators to go after our sons and our daughters," Trump said at a rally in North Carolina last week.
The Harris campaign in a statement to Reuters portrayed Trump as an extremist whose administration separated thousands of migrant families and who helped sink the bipartisan border security bill in the U.S. Senate - messaging in line with Biden's approach over the past year.
"There's only one candidate in this race who will fight for real solutions to help secure our nation's border, and that's Vice President Harris," campaign spokesperson Kevin Munoz said in a statement.
Some immigration advocates hope that Harris - herself the daughter of Indian and Jamaican immigrants - would better understand the humanitarian side of the issue.
Harris was instrumental in the Biden administration's rollout of a program in June to offer a path to citizenship to immigrants in the U.S. illegally who are married to U.S. citizens, two people familiar with the matter said.
Daniel Suvor, Harris' chief of policy between 2014 and 2017 when she was California attorney general, pointed to her efforts to marshal legal representation for unaccompanied immigrant children - even though immigration was not explicitly part of her portfolio.
She took it on herself to learn about the application process for special visas for victims of abuse, Suvor said. And she teamed up with Brad Smith, then the general counsel for Microsoft and co-founder of the advocacy group Kids in Need of Defense, and started calling law firms.
