WASHINGTON (AP) — Sen. Bernie Sanders ended his presidential bid on Wednesday, making Joe Biden the presumptive Democratic nominee to challenge President Donald Trump in a general election campaign that will be waged against the backdrop of the coronavirus pandemic.

Sanders initially exceeded sky-high expectations about his ability to recreate the magic of his 2016 presidential bid, and even overcame a heart attack last October. But he couldn’t 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, who is backed by much of the party’s establishment, told supporters at a virtual fundraiser that 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.”

Trump sought to foment the tension among Democrats by tweeting Wednesday that the party stacked the race against Sanders. The president said the senator’s supporters “should come to the Republican Party.”

Sanders 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 Hillary Clinton. Despite winning 22 states in 2016, there were no guarantees he’d be a major presidential contender this cycle.

But Sanders used strong polling and solid fundraising — collected almost entirely from small donations made online — to quiet early doubters. Like the first time, 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 crowded and divided field of alternatives sunk around him.

But Biden won a crucial endorsement from influential South Carolina Rep. Jim Clyburn and a subsequent, larger-than-expected victory in South Carolina, which propelled him into Super Tuesday, 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.

The coronavirus outbreak essentially froze the campaign, 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.

Though he will not be the nominee, Sanders was a key architect of many of the social policies that dominated the Democratic primary, including a “Medicare for All”  universal, government-funded health care plan, tuition-free public college, a $15 minimum wage and sweeping efforts to fight climate change under the “Green New Deal.”

Sanders began the 2020 race by arguing that he was the most electable Democrat against Trump. He said his working-class appeal could help Democrats win back Rust Belt states that Trump won in 2016, including Michigan, Wisconsin and Pennsylvania. But as the race wore on, the senator reverted to his 2016 roots, repeatedly stressing that he backs a “political revolution” from the bottom up under the slogan “Not me. Us.”

Sanders, 78, also faced persistent questions about being the field’s oldest candidate. Those were pushed into the spotlight on Oct. 1, when he was at a rally in Las Vegas and asked for a chair to be brought on stage so he could sit down. Suffering from chest pains afterward, he underwent surgery to insert two stents because of a blocked artery, and his campaign revealed two days later that he had suffered a heart attack.

A serious health scare that might have derailed other campaigns seemed only to help Sanders as his already-strong fundraising got stronger and rising stars on the Democratic left, including Rep. Alexandria Ocasio-Cortez, endorsed him. Many supporters said the heart attack only strengthened their resolve to back him.

Massachusetts Sen. Elizabeth Warren outshone him throughout much of the summer, but Sanders worked his way back up in the polls. The two progressive candidates spent months refusing to attack each other, though Sanders offered a strong defense of Medicare for All after Warren offered a plan for a transition to it that would take years.

But they clashed bitterly, if briefly, in January, when Warren said that Sanders had suggested during a 2018 private meeting that a woman couldn’t be elected president. Sanders denied saying that, but Warren refused to shake his outstretched hand after a debate in Iowa.

Warren left the race after a dismal Super Tuesday showing in which she finished third in her own state. Any lingering tension seemed to fade by Wednesday when Warren tweeted her thanks to Sanders for “fighting so relentlessly for America’s working families.”

With the leading progressive now out of the race, Biden moved to appeal to their supporters on Wednesday.

“I hope you will join us,” he said in a statement. “You are more than welcome. You’re needed.”

But Sanders made clear that while he is exiting the campaign, he will still be a force.

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

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Catch up on the 2020 election campaign with AP experts on our weekly politics podcast, “Ground Game.”