If Joe Biden were to step aside and allow someone else to take his place, here are six potential successors.

Joe Biden's performance in the presidential debate against Donald Trump has been described as a disaster. On several occasions, he stumbled, froze, misspoke, and stared blankly. Members of his own party are concerned, but the president is determined not to withdraw from the race. He has reportedly promised to return for a second debate with Trump.

Biden won the Democratic primary elections earlier this year. However, this does not officially establish him as the party's presidential candidate. That will happen only after he is endorsed at the 2024 Democratic National Convention in Chicago, which is set to take place from August 19 to 22.

US intel: Russia acting against Biden; China opposes Trump

There is currently no formal mechanism in place to replace Biden as the presumptive nominee. There is only one option: Biden should step aside and allow the delegates he won in the primaries to choose someone else. Delegates are not legally required to vote for the primary winner, but they are encouraged to vote in a way that "in all good conscience reflects the sentiments of those who elected them,".

However, if a situation arises where Biden were to step aside and let someone else replace him, here are six people who might potentially take his place:

1) Kamala Harris: Harris, the US vice president, would be the most obvious choice, though she has frequently been chastised for being unable to shape her own role in the Biden administration. She also receives low approval ratings. That being said, if Biden decides to resign, Harris will automatically become president.

2) Gavin Newsom: The California governor recently dismissed talk of being considered as an alternative to Biden as a nominee, calling it "nonsensical speculation." However, he has been known to support Democrats in elections outside of his home state and could potentially replace Biden.

3) J B Pritzker: Pritzker, the governor of Illinois, would be one of Biden's most wealthy replacements. He codified the right to abortion in his state, declaring it a "sanctuary state" for those seeking abortions. He also legalised recreational marijuana and has taken a strong stance on gun control.

4) Dean Phillips: Philips was a candidate during the Democratic primaries earlier this year. Although he did manage to pick some supporters, he did not win any contest, having failed to impress the broader party.

5) Sherrod Brown: Brown would be the oldest of the alternatives to Biden. However, the 71-year-old is still seven years younger than former president Trump. He has been a strong voice on labour rights and protections. He has also notably defended IVF and abortion.

6) Michelle Obama: Obama has long been thought to be a long shot for the Democratic presidential candidature in 2024. She has never indicated a strong desire to run, though. According to Betfair, Obama has a 16/1 (5.9 percent) probability of being the Democrats' next presidential nominee. Her staff previously informed NBC News in March that she would support Biden in the 2024 election. "As former first lady, Michelle Obama has stated several times over the years that she will not be running for president," the office said in a statement. "Mrs. Obama supports President Joe Biden and Vice President Kamala Harris' reelection campaign."