Many US Democrats — and anyone who dreads the thought of a second Donald Trump presidency — were no doubt relieved when Joe Biden on Sunday night (local time).
Shortly after announcing his exit, the 81-year-old incumbent praised vice-president Kamala Harris as an "extraordinary partner" and endorsed her as the Democratic candidate.
Harris thanked Biden for "selflessly" stepping down as she vowed to "earn and win" her party's nomination ahead of the November election.
Kamala Harris thanked Joe Biden for his decades of service and said his legacy was "unmatched in modern American history". Source: AAP / Allison Joyce
Harris is a frontrunner candidate for her party's ticket, but is the US ready for its first female president and what barriers would Harris need to overcome to beat Trump?
Who is Kamala Harris?
The 59-year-old Harris, the daughter of a Jamaican father and an Indian mother, is a trailblazer.
She was the first Black person and the first woman to serve as California's attorney-general and then was the first US senator of South Asian descent. Now she is .
During her career as a prosecutor, Harris had a reputation for being tough — a trait she could use to her advantage in a campaign expected to focus on crime and immigration.
Some progressive Democrats have been critical of the punishment she meted out for what they see as minor offences, saying this approach disproportionately affected minorities.
While her transition to the White House has proved difficult, she has led the party on abortion rights, an issue that resonates with younger voters and the Democrats' progressive base.
Harris's proponents argue she could energise young voters, consolidate Black support, and bring sharp debating skills to prosecute the political case against the former president.
Sexism, racism and Harris's record
Supporters of Harris argue she has already weathered unfair attacks related to her race and gender and is prepared for more.
"America has a history of racism, sexism, so I'm sure that will factor into this conversation, factor into her campaign," said Jamal Simmons, a former Harris aide.
But there's a flip side to this.
Black voters could be galvanised if Harris is put at the top of the ticket, and women, including some who regret not voting for Hillary Clinton in 2016, would back her as well, he said.
"It's also true that she will benefit from her race and her gender, that many African Americans may rally to her candidacy," he said.
Kamala Harris could soon become the first Black woman to head a major party's presidential ticket after President Joe Biden ended his re-election bid. Source: AAP / Jacquelyn Martin
"That to me is reflective of America's past. She is reflective of America's now and future," Brown said.
However, others like Democratic representative Alexandra Ocasio-Cortez, who previously questioned the viability of replacing Biden so close to the election, argue there is "no safe option".
"If you think that there is consensus among the people who want Joe Biden to leave that they will support Kamala — Vice-President Harris — you would be mistaken," she said on Instagram.
However, following Biden's announcement, Ocasio-Cortez has pledged her "full support" to Harris's bid for the nomination.
One former Democratic lawmaker, speaking on condition of anonymity, said he thought Harris's record, rather than her race, made choosing her a bigger risk.
"I think the race thing is just a compounding factor or an exacerbating factor," the former lawmaker said.
Harris was plagued by staff turnover at the beginning of her vice-presidency and was criticised for what some saw as little progress on her portfolios of protecting voting rights and stemming migration from Central America.
"Any of it's going to be a gamble, but I like the odds with another candidate (apart from Biden), even if that means Kamala at the top of the ticket."
The poll numbers on Trump and Harris
Harris and Trump were tied with 44 per cent support each in a July 15-16 Reuters/Ipsos poll, conducted immediately after the against Trump.
Trump led Biden 43 per cent to 41 per cent in that same poll, though the 2 percentage point difference was within the poll's 3 percentage point margin of error.
Harris's approval ratings, while low, are slightly higher than Biden's.
According to polling outfit Five Thirty Eight, 38.6 per cent of Americans approve of Harris while 50.4 per cent disapprove. Biden has 38.5 per cent approval and 56.2 per cent disapproval.
