WASHINGTON (AP) — Sen. Bernie Sanders, who saw his once strong lead in the Democratic primary evaporate as the party’s establishment lined swiftly up behind rival Joe Biden, ended his presidential bid on Wednesday, an acknowledgment that the former vice president is too far ahead for him to have any reasonable hope of catching up.

The Vermont senator’s announcement makes Biden the presumptive Democratic nominee to challenge President Donald Trump in November.

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.

Sanders initially exceeded expectations about his ability to recreate the magic of his 2016 presidential bid, and even overcame a heart attack last October. But he found himself unable to convert unwavering support from progressives into a viable path to the nomination, with "electability” fears fueled by questions about whether his democratic socialist ideology would be palatable to general election voters.

“The path toward victory is virtually impossible,” Sanders told supporters Wednesday. “If I believed we had a feasible path to the nomination I would certainly continue the campaign, but it’s just not there.”

He called Biden a “very decent man” but didn’t offer an explicit endorsement of the former vice president. Sanders said his name would remain on the ballot in states that have not yet held primaries so he can gain more delegates and “exert significant influence” on the Democratic platform.

Biden credited Sanders for creating “a movement” and appealed to his progressive supporters.

“I see you, I hear you, and I understand the urgency of what it is we have to get done in this country,” Biden said. “I hope you will join us. You are more than welcome. You’re needed.”

Sanders used strong polling and solid fundraising — collected almost entirely from small donations made online — to quiet early doubters at the beginning of the 2020 campaign season. Like 2016, he attracted widespread support from young voters and made new inroads within the Hispanic community, even as his appeal with African Americans remained weak.

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 on March 3, when he won 10 of 14 states.

In a matter of days, Biden's former Democratic rivals lined up to endorse him. His 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.

Things only got worse for Sanders the following week when he 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.

The coronavirus outbreak essentially froze the campaign at that point, preventing Sanders from holding the large rallies that had become his trademark and shifting the primary calendar. It became increasingly unclear where he could notch a victory that would help him regain ground against Biden.

Sanders made clear Wednesday that while he is exiting the campaign, he will keep pushing for progressive principles.

“Please stay in this fight with me," he told supporters. "The struggle continues.”