After weeks of constant pressure to drop his bid for re-election, President Biden suddenly announced his withdrawal from the presidential race despite earlier assurances that he would remain.

“I believe it is in the best interest of my party and my country that I step down and focus solely on fulfilling my duties as President for the remainder of my term“, said Biden in a letter that he posted on social networks.

Along with announcing his resignation, Joe Biden publicly offered his support to Vice President Kamala Harris as the Democratic nominee for president. “Today I want to offer my full support for Kamala to be our party’s nominee,” Biden said in another post.

In the wake of Biden’s resignation, the Kamala Harris she proceeded shortly thereafter to announce her candidacy for the Democratic nomination. “I am honored to have the support of the president and my intention is to win the nomination for the president,” he said.

The next few days will prove pivotal as Democratic leaders try to unite all of the party’s disparate voices around Kamala Harris.

Who will replace Biden?

Vice President Harris is the most likely candidate to replace Biden in the presidential race, as the US president has endorsed her, but many in the party have already said they will accept her as a candidate.

But Harris’ candidacy isn’t guaranteed just because she has Biden’s endorsement and is his running mate. The Democratic Party is free to choose a different replacement if its members rally around another candidate. Even then, the nominee will not be made official until the delegates vote.

How will a new candidate be selected?

Unlike a president’s resignation, which automatically advances the vice president to the White House, Biden’s withdrawal from the race doesn’t mean Harris will be the official nominee. Most Democrats expect her to be his replacement, but delegates who choose the presidential nominee at the Democratic National Convention are free to vote for whichever candidate they want.

If Democrats fail to rally behind someone, they will be headed to an open convention for the first time since 1968. The process is expected to spark behind-the-scenes deliberations as would-be candidates try to win the support of independent delegates. However, Democrats will likely try to avoid such a development by attempting to consolidate support behind one person before the convention.

How quickly could a candidate be selected?

Although Biden and the party have endorsed Harris, no one becomes an official nominee until delegates vote. Before Biden withdrew from the race, the Democratic National Committee ehas decided to hold a virtual vote in the first week of August to nominate its presidential candidate. If canceled, then the candidate will be selected at the convention, which is scheduled to begin on August 19.

How is Kamala Harris trending in the polls against Trump?

Although Biden endorsed Kamala Harris, recent polls show little difference between Biden and Donald Trump.

In an average of Washington Post eleven polls after the debate, Trump was leading Biden by an average of 1.9%, compared to 1.5% for Harris. Four polls showed the Vice President doing slightly better than Biden. However, in four others she collected worse percentages, while in three more there was no difference in her dynamics compared to that of Biden.

A Washington Post-ABC News-Ipsos poll this month found that 44 percent of Americans overall said they would be “satisfied” if Biden withdrew and Harris became the Democratic nominee, including 70 percent of Democrats.

In the same poll, 29% of Democrats and independents said they support Kamala Harris’ candidacy if Biden resigns, while 7% cited California Gov. Gavin Newsom, 4% Michelle Obama. Half the Democrats named none.

What will happen at the Democratic convention?

It will be crucial if the party rallies around Harris and no one challenges her candidacy. In that case, delegates are likely to vote for her at the convention, as they would for Biden.

If, however, there are many candidates, then an open conference will be held with delegates free to vote for the candidate of their choice. In the first round of voting, only accredited representatives—about 3,900—can vote. If no candidate gets a majority, then superdelegates — about 700 party leaders and elected officials — can vote in subsequent rounds until a candidate is chosen.

Has this happened before?

Yes, when on March 31, 1968, President Lyndon B. Johnson dropped out of the presidential race. It was the last time Democrats held an open convention.