Ms Harris is yet to be officially nominated, and she will need a running mate when Democratic party delegates vote next month at a convention in Chicago to officially confirm who is on the ticket.

Historically, vice-presidents are picked to complement a candidate and strategists believe for that reason she may pick a white man from a swing state.

The following names are reported to be in the mix.

Josh Shapiro has seen high approval ratings since he was elected in 2022 in a swing state Trump narrowly carried in 2016. The governor, who previously served as the state’s attorney general, has worked across party lines during his tenure.

He made national headlines last year after quickly rebuilding a collapsed bridge on a crucial Philadelphia highway – a major political victory for a first-term governor. The speedy repair was hailed by many as the perfect infrastructure talking point for a potential 2028 presidential candidate.

Mr Shapiro said Mr Biden was one of the “most consequential presidents in modern history” and would “do everything I can to help elect Kamala Harris as the 47th President of the United States”.

Mr Beshear has carved out a successful career as the Democratic leader of a deep-red state. He won his first term in 2019 and was re-elected in 2023, campaigning on key issues for the party like supporting public education and protecting reproductive rights.

His popularity in Kentucky is crucial, given that the state voted for Trump by a margin of more than 25 percentage points in 2020.

At 46, Mr Beshear is also one of the youngest governors in the country.

He has been floated around as a potential pick to lead the party in the 2028 presidential election. But now with Mr Biden out of the picture, Mr Beshear’s run for the White House could come much sooner.

Former astronaut and combat veteran Mr Kelly is a possible contender given his success in Arizona, a key swing state, including a decisive victory in the 2022 mid-term election.

Trump has been leading Biden in the state’s polling, so recruiting Mr Kelly could boost the Democrats’ popularity at a crucial moment in the race.

He is the husband of former House Representative Gabby Giffords, who was seriously wounded in a 2011 mass shooting in Arizona. With gun violence being a major campaign issue for Democrats, Mr Kelly’s personal story could resonate with voters.

Gretchen Whitmer, the two-term governor of Michigan, is an increasingly popular Midwest Democrat who many pundits speculate will run for president in 2028.

She has campaigned for Mr Biden in the past and has not been shy about her political aspirations.

She told The New York Times that she wants to see a Generation X president in 2028, but stopped short of suggesting that she might fill that role.

In 2022, she led a campaign that left Michigan Democrats in control of the state’s legislature and the governor’s mansion.

That allowed her to enact a number of progressive policies, including protecting Michigan abortion access and the passage of gun safety measures.

Ms Whitmer quickly stated after Mr Biden’s withdrawal that her job “will remain the same… doing everything I can to elect Democrats and stop Donald Trump”.

She endorsed Ms Harris on Monday, writing on X that the vice-president has her “full support”.

“In Vice President Harris, Michigan voters have a candidate they can count on to lower their costs, protect their freedoms, and build an economy that works for working people,” she said.

Ms Whitmer also announced she would be serving as co-chair of the Harris campaign.

California’s governor is one of the Biden administration’s fiercest surrogates.

He is often listed as a possible 2028 candidate, but many Democratic pundits had suggested he could be in the race to replace Mr Biden.

Mr Newsom raised his national profile in recent years by being a key party messenger on conservative media, and via a debate against Florida Governor Ron DeSantis last year.

He stood by the president before his announcement. He travelled to Washington to attend meetings in July with Mr Biden and other top Democratic governors, and headlined a Biden campaign event in Michigan on the 4 July.

Mr Newsom again praised Mr Biden as a “selfless” president after his withdrawal, and said he backed the “fearless” and “tenacious” Ms Harris to face Trump.

Mr Cooper is another Democrat who has seen great success in a state that has voted for Trump twice, both in 2016 and in 2020.

North Carolina is seen as a big opportunity for Democrats given its rapidly growing population around its major centres, Charlotte and Raleigh. Ms Harris herself has travelled to the state several times this year in a bid to shore up support for her party.

Along with his popularity, Mr Cooper brings with him a deep wealth of knowledge, having served in public office since 1987.

He sat in both the House and the Senate, and was later elected attorney general for the state – a job he had for 16 years thanks to three successful re-election bids.

Mr Cooper then moved on to serve as governor, elected at first in 2017 and again in 2020.

He has already voiced his support for Ms Harris’ presidential bid, writing on social media: “I’ve known (the vice-president) going back to our days as AGs, and she has what it takes to defeat Donald Trump”.

It is no secret that Pete Buttigieg has presidential aspirations.

He ran in 2020 and is often touted as one of the Biden administration’s best communicators.

Mr Buttigieg has managed a number of public crises during his time as transportation secretary.

He helped to oversee the government response to the East Palestine train derailment in Ohio, the Baltimore Bridge collapse and Southwest Airlines’ scheduling crisis in 2022.

Mr Buttigieg stated on Twitter/X that Mr Biden had “earned his place among the best and most consequential presidents in American history”.

He said he would do “all that I can to help elect Kamala Harris the next President”.

JB Pritzker, the governor of Illinois, has raised his profile in recent years by going after Trump and defending Mr Biden.

The billionaire businessman – heir to the Hyatt hotel chain – is quick to post criticism of Trump on social media.

After the debate he called Trump a “liar” and said he is a “34-count convicted felon who cares only about himself”.

Like Ms Whitmer, Mr Pritzker has a track record of completing agenda items on progressive Democrats’ to-do lists on issues like abortion rights and gun control.

He said Mr Biden had run “one of the most accomplished and effective presidencies of our lifetime”.

Mr Pritzker endorsed Ms Harris on Monday, writing on X that Mr Biden’s decision to step down came as a “genuine surprise”. He added that the vice-president is the party’s best chance to defeat Trump.

“Vice President Harris has proven, at every point in her career, that she possesses the skills, strength, and character to lead this country and the vision to better lives of all Americans,” he said.

The list of potential nominees to the ticket stretches beyond these Democrats, as the party has developed a deep bench of talent.

Maryland Governor Wes Moore found himself in the spotlight in recent months following the collapse of the Francis Scott Key Bridge in Baltimore.

Senators Amy Klobuchar and Cory Booker have run for president in the past and have some name recognition among Democrats.

And Georgia Senator Raphael Warnock, who won a closely contested Senate race in a swing state.