• Democratic Party delegates are set to vote for their presidential nominee in a virtual roll call in early August, before the party's convention.
• President Joe Biden's endorsement of Kamala Harris bolsters the view of many pundits and experts who see her as the likeliest choice to replace him.

This story was updated after President Joe Biden announced his decision to exit the presidential race on July 21.

President Joe Biden announced Sunday that he would drop out of the presidential race and endorsed Vice President Kamala Harris as the candidate to replace him.

The president's decision came as he isolated with Covid at his Delaware beach house. In the wake of his damaging debate against Donald Trump, Biden faced mounting pressure from Democrats — in private and in public — calling on him to step down.

While he had initially rejected the calls to step aside, Biden said Tuesday that should a "medical condition" emerge, it could force him to rethink his decision to stay in the race.

On Wednesday, Biden, 81, tested positive for Covid-19. His doctors say his symptoms are mild and that he is recovering steadily.

Here is what happens next.

Delegates

After breezing through the primary virtually unopposed, Biden won almost all of his party's 4,000-plus delegates, who are selected in large part because of their loyalty and support for their chosen candidate.

Since Biden ended his campaign before voting began, those delegates can cast their ballots for a new candidate.

The delegates are set to vote for their presidential nominee in a virtual roll call in early August, before the Democratic National Convention. According to the DNC rules, if no candidate wins a majority on that first ballot, then the more than 700 "superdelegates" can join in subsequent votes.

The voting would then continue until one candidate won a simple majority of delegates.

The likeliest alternative

Biden's endorsement of Harris bolsters the view of many pundits and experts who see her as the likeliest choice to replace him.

"The vice president is the logical choice, obviously," said Meena Bose, director of the Peter S. Kalikow Center for the Study of the American Presidency at Hofstra University, in an interview.

Bose noted that Harris, 59, has already been vetted, when she joined Biden's campaign in 2020. What's more, the fundraising war chest that the Biden campaign has amassed in the current election cycle would transfer to her if she took over the ticket.

Harris, like Biden, has struggled with low approval ratings throughout the last four years. And Republicans are already deploying attacks against her, accusing her of failing in her job as the administration's "border czar" — even though she was not given that task.

Other high-profile Democrats, such as California Gov. Gavin Newsom or Michigan Gov. Gretchen Whitmer, have been floated as potentially stronger alternatives to Harris if Biden were no longer in the race. But almost all of those figures have already said they would not run for president in 2024.

There is also a risk that leap-frogging the vice president in favor of another candidate could spark a bitterly contested party convention, something Democrats surely want to avoid — especially after the Republican convention's display of near-total unity behind Trump this week.

"Time is really tight and it's difficult to mount a campaign for anyone other than the vice president," Bose said.

With Harris, it's "not like you're just anointing some stranger," said Christina Bellantoni, the director of USC Annenberg's Media Center and a former longtime journalist in Washington.

"You could make the argument that she could carry on the legacy, that she is the obvious next choice, all of those things," she said.