As soon as Joe Biden announced his exit from the US presidential race and vice-president Kamala Harris pledged to replace him on the ticket, the race to become her running mate began.
With just over three months until the November election, the candidate Harris campaigns alongside will be critical to beating Republican candidate Donald Trump in key swing states, experts told SBS News.
Biden's exit has scrambled Trump's campaign strategy of focusing on the 81-year-old's weaknesses and gives the Democrats a great chance to recalibrate, said David Smith, associate professor at the United States Studies Centre at the University of Sydney.
"Democrats do have an opportunity to create a really fresh ticket which could motivate people who otherwise might've avoided the race altogether," he told SBS News.
In the 24 hours since Harris announced her intention to seek the nomination, several vice-presidential hopefuls have been quick to endorse her candidacy and rally behind her.
There are several frontrunners, each with various strengths and weaknesses.
Gretchen Whitmer
Gretchen Whitmer is the governor of Michigan, a key swing state for the election, offering 15 of the 270 electoral college votes needed to elect the president.
The 52-year-old Democratic star has strong national recognition and has been outspoken on issues of abortion rights, infrastructure and health care.
"One of the benefits of an all-female ticket could be that it moves the election right back onto reproductive rights, which is by far the Democrat's strongest issue in this election," Smith said.
"Trump not only didn't choose a woman as his vice presidential candidate, he chose a man who has supported a national abortion ban and has supported a postal ban on abortion drugs so quite an extremist by American standards."
Others like Morgan Rees, lecturer in policy and politics at Queensland University of Technology School of Justice, said Whitmer is unlikely to be chosen
Rees said a Harris-Whitmer ticket would be a "double barrier", as Harris already has to overcome "some major racial and socialistic obstacles just to get across alone".
Josh Shapiro
Rodrigo Praino, a professor of politics and policy at Flinders University, said he had put "most his confidence" into Josh Shapiro, the governor of Pennsylvania.
The 51-year-old former attorney-general and country commissioner is very popular in Pennsylvania, a swing state with 16 electoral college votes, said Praino, the director of the Jeff Bleich Centre for Democracy and Disruptive Technologies.
"Being able to secure Pennsylvania is one of the possible ways to secure the White House," Praino told SBS News.
Smith said Shapiro also had appeal with Trump voters, pointing to May polling by the Inquirer that showed more than a third of Republicans, 42 per cent, approved of his leadership.
However, Shapiro, who is Jewish, is also a staunch backer of Israel — an issue currently dividing Democratic voters.
Mark Kelly
As a former NASA astronaut, Mark Kelly has the potential to captivate the imagination of voters with his "compelling story", Smith said.
The 60-year-old senator from Arizona, a battleground state that holds 11 electoral college votes, is a former Navy officer who is respected for his work and scientific expertise.
The hotly contested state borders Mexico and has traditionally favoured Republicans, but Biden won the state in 2020.
Kelly has been an advocate for gun reform after his wife, former US representative Gabby Giffords, was left severely injured by a shooting.
Pete Buttigieg
Pete Buttigieg, the Biden administration's transport secretary, is also a possible pick.
At 42, the previous mayor of South Bend in Indiana is the youngest frontrunner candidate, which could appeal to centrist and Midwest voters.
Smith said Buttigieg is media savvy and often performs well on conservative shows like Fox News — something that pleases his party colleagues.
"If he was the vice-presidential candidate, he would be the first openly gay man on a presidential ticket in the United States," Smith said.
"Perhaps the drawback with him is that in the past he hasn't done very well with minority voters, and certainly getting minority voters back is one of the real priorities for the Democratic party."
