Who could replace Biden as the Democratic presidential nominee?

U.S. President Joe Biden and the White House have been on the defensive amid growing doubts about whether he can win the November election.

The poor debate performance led to growing panic and confusion about Biden's candidacy.

The ongoing, and now public, debate over how to maintain Democratic control of the White House has also raised questions about who would replace Trump as a presidential candidate if he decided to leave office.

The move, while unlikely, could create a logistical nightmare and spark ugly partisan fighting within the Democratic Party just months before voters cast their ballots.

There are several ways to replace the president, but with just over four months until the election, it is unlikely that Biden, 81, would withdraw from the race.

But as the debate continues, public support for Biden's running mate, Kamala Harris, appears to be growing, and other names of potential candidates are emerging.

If Biden were to step down, here are some potential replacements:

Vice President Kamala Harris, who has already been mentioned as a candidate, is the obvious choice to succeed Biden and is growing in popularity.

As vice president, she became the face of her administration's campaign to protect reproductive rights after the Supreme Court overturned Roe v. Wade.

Ms Harris proved to be a staunch ally of the president and fiercely defended his performance in the debate, acknowledging after the debate that the president “got off to a slow start” but then insisting that he gave more substantive answers than Mr Trump.

Days after the debate, Ms Harris reiterated her support for Mr Biden amid growing concern about whether the president could retain his top spot among the candidates.

“Joe Biden is our candidate. We beat Trump once and we're going to beat him again, period,” she said Tuesday.

“I am honored to be Joe Biden's running mate.”

Although Harris enjoys high public profile as vice president, she has struggled with low approval ratings during her term in office.

According to an average of polls tracked by FiveThirtyEight, 49% of Americans disapprove of Harris, while 39% approve.

Harris could also get a leg up among potential presidential candidates with a prime-time moment to face off against Trump's vice presidential pick – the BBC's US media partner CBS is set to host a vice presidential debate ahead of the Democratic National Convention in August.

Gretchen Whitmer, a two-term Michigan governor and Democrat who is gaining popularity in the Midwest, is predicted by many observers to run for president in 2028.

She has campaigned for Biden in the past and has made no secret of her political ambitions.

She told The New York Times that she would like to see a Gen Xer become president in 2028, but did not suggest that she might play that role.

In 2022, she led the campaign to get Michigan Democrats control of the state legislature and the governor's mansion.

Her political dominance has allowed her to enact a number of progressive policies, including protecting abortion access in Michigan and passing gun safety measures.

California Gov. Gavin Newsom has been one of the Biden administration's most vocal apologists, frequently appearing on cable news networks to praise Biden.

But Newsom has political ambitions of his own.

He has often been mentioned as a possible candidate for the 2028 presidential election, and many Democratic experts say he would be an attractive alternative to Biden.

Newsom has risen to national prominence in recent years as a key messenger for his party in conservative media and through his debate with Florida Gov. Ron DeSantis last year.

It's no secret that Secretary of Transportation Pete Buttigieg has presidential ambitions.

He ran for president in 2020 and is often praised as one of the Biden administration's best communicators.

Buttigieg has dealt with a number of public crises during his time as transportation secretary.

He helped oversee the administration's response to the East Palestine train derailment, the Baltimore bridge collapse and the 2022 Southwest Airlines scheduling crisis.

Pennsylvania Gov. Josh Shapiro has maintained high approval ratings since winning in 2022 in a battleground state that Trump narrowly won in 2016.

The governor, a former state attorney general, has worked across party lines during his tenure.

He made national headlines last year for quickly rebuilding a collapsed bridge on a key Philadelphia highway, scoring a major political victory for a first-term governor.

The swift repairs were hailed by many as the perfect infrastructure talking point for 2028 presidential candidates.

Illinois Governor J.B. Pritzker has gained publicity in recent years for attacking President Trump and defending Biden.

The billionaire businessman and heir to the Hyatt hotel chain has been a frequent critic of President Trump on social media.

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

Like Whitmer, Pritzker has a track record of achieving agendas on progressive Democrats' to-do list on issues such as abortion rights and gun control.

The Democratic Party has a strong roster of potential future presidential candidates, so the list of candidates extends beyond these Democrats.

Andy Beshear, the two-term Democratic governor of deeply conservative Kentucky, has been in the national spotlight since his re-election last year.

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

Senators Amy Klobuchar and Cory Booker are often mentioned because they have run for president in the past and have some name recognition among Democrats.

Georgia Sen. Raphael Warnock, who won a closely contested Senate election in a battleground state, has also been mentioned as a possible successor to Biden.

A Reuters IPSOS poll released on Tuesday said Michelle Obama is the only person who could beat President Trump in November, even though the former first lady has repeatedly said she has no presidential ambitions.