Less than a week after he dropped out of the Democratic White House race, U.S. Sen. Bernie Sanders formally endorsed Joe Biden for president on Monday.

“I am asking all Americans, I’m asking every Democrat, I’m asking every independent, I’m asking a lot of Republicans to come together in this campaign to support your candidacy, which I endorse,” Sanders said via livestream.

Sanders dropped out of the race April 8, ending weeks of speculation about his campaign as he lost primary after primary to the former vice president.

Biden, who is backed by much of the party’s establishment, told supporters at a virtual fundraiser last week he had a “short conversation” with Sanders on Wednesday.

“He didn’t just run a political campaign. He created a movement,” Biden said. “That’s a good thing for our nation and our future. His campaign has ended, but I know his leadership will continue.”

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The 78-year-old senator began his latest White House bid facing questions about whether he could win back the supporters who chose him four years ago as an insurgent alternative to the party establishment’s choice, Hillary Clinton.

Despite winning 22 states in 2016, there were no guarantees he’d be a major presidential contender this cycle, especially as the race’s oldest candidate.

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Sanders, though, used strong polling and solid fundraising — collected almost entirely from small donations made online — to more than quiet early doubters. Like the first time, he attracted widespread support from young voters and was able to make new inroads within the Hispanic community, even as his appeal with African Americans remained small.

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Sanders amassed the most votes in Iowa and New Hampshire, which opened primary voting, and cruised to an easy victory in Nevada — seemingly leaving him well positioned to sprint to the Democratic nomination while a deeply crowded and divided field of alternatives sunk around him.

But a crucial endorsement of Biden by influential South Carolina Rep. Jim Clyburn and a subsequent, larger-than-expected victory in South Carolina propelled the former vice president into Super Tuesday, when he won 10 of 14 states.

In a matter of days, his top former Democratic rivals lined up and announced their endorsement of Biden. The former vice president’s campaign had appeared on the brink of collapse after New Hampshire but found new life as the rest of the party’s more moderate establishment coalesced around him as an alternative to Sanders.

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Things only got worse the following week when Sanders lost Michigan, where he had campaigned hard and upset Clinton in 2016. He was also beaten in Missouri, Mississippi and Idaho the same night, and the results were so decisive that Sanders headed to Vermont without speaking to the media.

Sanders had scheduled a rally in Ohio but canceled it amid fears about the spread of the coronavirus. The outbreak kept him home as his campaign appeared unsure of its next move. The senator addressed reporters the following day but also sounded like a candidate who already knew he’d been beaten.

“While our campaign has won the ideological debate, we are losing the debate over electability,” Sanders said then.