Hours after Joe Biden made the stunning decision to end his bid for re-election, Vice-President Kamala Harris — with Biden's endorsement — announced that she is running for president in the 2024 general election against Donald Trump.

Harris, a former prosecutor and California senator who first ran for president in 2020 before she was picked as Biden's running mate, said she was "honoured to have the president's endorsement."

"My intention is to earn and win this nomination," wrote Harris in a statement. She is not guaranteed the nomination until she is voted in by delegates during the Democratic National Convention next month.

"Over the past year, I have travelled across the country, talking with Americans about the clear choice in this momentous election. And that is what I will continue to do in the days and weeks ahead," she said.

If elected, Harris's presidency would be historic, making her the first woman, first Black woman and first South Asian to serve as president. She's led the Biden administration's response on key issues including immigration, voting rights and abortion.

But she has an uphill battle ahead, having struggled with public image issues and poor polling throughout her vice-presidency. 

What she achieved, how she was criticized

Harris, the daughter of Indian and Jamaican immigrants, first ran for president in 2020 after serving in the U.S. Senate and as attorney general of California. Her presidential campaign was marred by low polling and messaging issues, leading her to drop out of the race before the primaries began.

She continued to poll poorly during her first year as vice-president, amid a growing perception that she had been cast aside by the Biden administration that year — to the point that White House press secretary Karine Jean-Pierre released a statement stressing that Harris was a "vital partner" to Biden.

Harris was further challenged by early turnover among her staff. The Washington Post called it an "exodus," and a Politico investigation found that aides and senior officials were "experiencing low morale, porous lines of communication and diminished trust."

WATCH | How will Harris handle Trump — and vice-versa: 

Joe Biden endorses Kamala Harris. How would she fare against Donald Trump?

U.S. President Joe Biden has thrown his support behind Vice-President Kamala Harris after ending his re-election campaign on Sunday. Political science professor Chris Galdieri reacts to Biden’s backing of Harris, while Republican strategist Chip Felkel looks at how she stacks up against Trump.

Early into her vice-presidency, Harris was appointed by the Biden administration to lead its immigration response at the southern U.S.-Mexico border, and was tasked with understanding what was driving mass migration from Guatemala, Honduras and El Salvador.

One of her most significant achievements came when she secured $4.2 billion US in private-sector investments for job creation and economic development in Central America. The initiative was meant to quell the flow of migrants out of those countries and into the U.S., and the administration has said that it's on track to reach its goals in the region.

Yet Harris was criticized on both sides of the aisle for delaying a trip to the Mexican border, and some conservatives called her a failed "border czar" who had dropped the ball as the humanitarian crisis at the border intensified.

Another key issue in Harris's vice-presidential portfolio is abortion rights, for which she became an especially outspoken advocate after the June 2022 overruling of Roe v. Wade.

At the beginning of this year, she launched a "fight for reproductive freedoms" tour that was meant to push for further access to abortion across the country, while mobilizing voters on abortion issues ahead of the election. 

She has also been outspoken on lowering prescription drug costs, promoting gun reform, and has led efforts to legislate voting rights protections. The latter assignment was ultimately stalled without the support of two Senate Democrats.

Some polling has shown Harris might be a stronger matchup against Trump than Biden was. Another poll has shown that most Democrats think she would make a good president, with about six in 10 saying they believe Harris would do a good job as president. Two in 10 say they don't believe she would, and another two in 10 said they don't know enough to respond.

In that same poll, there was broader skepticism among Americans regardless of party. Only three in 10 U.S. adults said Harris would do well in the top job. Her favourability rating is similar to Biden's, but the share of voters who have an unfavourable opinion of her is lower.

The poll of 1,253 adults was conducted July 11-15, 2024, with a margin of error of +/- 3.8 percentage points.

A growing chorus of support

So far, Harris has been endorsed by Biden, former U.S. president Bill Clinton and Hillary Clinton, a former secretary of state. She has also received endorsements from the Congressional Black Caucus, and a growing group of House representatives and senators, including Massachusetts Sen. Elizabeth Warren and Virginia Sen. Tim Kaine.

Notably, former president Barack Obama and his wife Michelle had not yet endorsed Harris as of late Sunday afternoon.

A lot of Democrats are increasingly realizing "that Vice-President Kamala Harris is probably the simplest and most straightforward alternative to Biden," said Chris Galdieri, a  political science professor at Saint Antselm College in New Hampshire. "It's literally her job to step in if Biden is not able to do the job."

There is also the question of who her running mate will be, assuming that she is the nominee. While Harris might appeal to Black and women voters, she will have less of a hold on important swing voter states like Wisconsin, Michigan and Pennsylvania.

She'll likely choose a candidate who can move the needle in regions where the Democrats are struggling.

"Will it be somebody who can appeal to those midwestern industrial states?  Will she look for somebody who can help Democrats in the southwest, where they've made inroads into places like Nevada and Arizona in the last few years? Or will she go for somebody who can help in the south?" Galdieri said.

Having spent four years working in the White House, Harris is probably best suited to articulate the case for the Biden administration's record and argue that she can continue their work in another term, he added.

Biden's support had been lagging among Black voters, who showed less enthusiasm for him during this election than they had during his initial 2020 run. Harris, by contrast, polls favourably among Black voters and will likely prove more popular among female voters, said Galdieri.

"I think for the Democrats to pass over the first woman vice-president, the first Black woman to serve as vice-president, would provoke a major rift with Black voters, particularly Black women who have become such an important bedrock constituency for the Democratic Party in recent years."