VICE-PRESIDENT Kamala Harris moved swiftly on Sunday to lock up the Democratic presidential nomination after Joe Biden stepped down from the campaign to be re-elected as the United States president.

After withdrawing from the campaign, Mr Biden threw his support behind his vice-president.

“Today I want to offer my full support and endorsement for Kamala to be the nominee of our party this year,” he said in another post on X. 

“Democrats: it’s time to come together and beat Trump.”

Aiming to put weeks of drama over Mr Biden’s candidacy behind them, prominent Democratic elected officials, party leaders and political organisations quickly lined up behind Ms Harris in the hours after President Biden announced he was dropping his re-election campaign.

In a statement, Ms Harris praised Mr Biden’s “selfless and patriotic act” in deciding to leave the race and said she intends to “earn and win” her party’s nomination.

“I will do everything in my power to unite the Democratic Party — and unite our nation — to defeat Donald Trump and his extreme Project 2025 agenda,” she said.

Mr Biden’s departure frees up his delegates to vote for whomever they choose. Ms Harris, whom Mr Biden backed after ending his candidacy, is so far the only declared candidate and was working to quickly secure endorsements from a majority of delegates.

If she is successful at securing the nomination, she must also pick a running mate and pivot a massive political operation to boost her candidacy instead of Mr Biden’s with just over 100 days until election day.

On Sunday afternoon, Mr Biden’s campaign formally changed its name to Harris for President, reflecting that she is inheriting his political operation of more than 1,000 staffers and a war chest that stood at nearly $96 million (£74m) at the end of June.

The vice-president quickly won endorsements from the leadership of several influential caucuses and political organisations, including the chairs of the Congressional Progressive Caucus, the Congressional Hispanic Caucus and the Congressional Black Caucus. 

If she wins November’s election, Ms Harris would be the first woman and first person of south Asian descent to be US president.

Former president Barack Obama held off on an immediate endorsement but pledged his support behind the eventual party nominee.

The Democratic National Committee’s chairman Jaime Harrison, said in a statement that the party would “undertake a transparent and orderly process” to select “a candidate who can defeat Donald Trump in November.”

The Democratic National Convention is scheduled to be held August 19-22 in Chicago.