Vermont Sen. Bernie Sanders announced on Wednesday he would suspend his campaign for the Democratic presidential nomination, bringing to an end a comeback bid four years in the making that saw him, briefly, become the frontrunner for the Democratic nomination.

But it was not meant to be.

“Together we have transformed American consciousness as to what kind of nation we can become,” Sanders said in livestreamed remarks from his home in Burlington, Vermont, where he has been in isolation for nearly a month due to the coronavirus pandemic.

After outlining what he called the victories of his campaign—advocating for minimum wage increases, universal healthcare, free college education and environmental justice, and railing against corporate influence in politics, mass incarceration and concentration of wealth among the richest people—Sanders said that he had made the “difficult and painful” decision that, despite his success among younger voters, victory was “virtually impossible.”

“This battle for the Democratic nomination will not be successful, and so today, I am announcing the suspension of my campaign,” Sanders said, congratulating former Vice President Joe Biden on becoming the party’s nominee-in-waiting.

Sanders also pointed to the coronavirus pandemic, which has wreaked havoc on the primary calendar and put voters at risk of infection, as another reason for dropping out.

“I cannot in good conscience continue to mount a campaign that cannot win, and which would interfere with the important work required of all of us in this difficult hour,” Sanders said. The Vermont senator vowed to stay on the ballot in upcoming primary states in order to gather delegates, a move he said will allow progressives to exert “significant influence over the party platform and other functions” at the Democratic National Convention.

Biden praised Sanders for doing something “rare” in politics. “He hasn’t just run a political campaign; he’s created a movement. And make no mistake about it, I believe it’s a movement that is as powerful today as it was yesterday,” the likely nominee wrote in a blog post.

Sen. Elizabeth Warren (D-MA), who declined to endorse a nominee after she ended a campaign that split the progressive vote, thanked Sanders “for fighting so relentlessly for America’s working families during this campaign.” She said his fight for progressive ideas had “moved the conversation and charted a path for candidates and activists that will change the course of our country and party.”

An unparalleled grassroots fundraising network and a progressive base fueled by his 2016 campaign made Sanders a top tier candidate throughout the 2020 campaign. He successfully pulled several of his rivals to the left and watched as many of them contorted themselves, unsuccessfully, to emulate his platform of democratic socialism.

But the progressive policies that inspired so many voters—universal government-run healthcare, tuition-free college, a wealth tax on the richest Americans—repelled many risk-averse Democratic voters who cared more about beating President Donald Trump than bringing down the system that enabled his rise.

Sanders’ decision to leave the race comes as the United States plunges deeper into a state of crisis, and as the federal and state government implement unprecedented measures aimed at containing the coronavirus pandemic. States of emergency have been declared, major sporting events, classes and gatherings both big and small have been canceled, and multiple states have issued shelter-in-place orders requiring that all but essential workers remain in their homes.

Officials in more than a dozen states took the extraordinary step of moving their state’s primaries over the health scare, effectively freezing the primary calendar until June and allowing the Vermont senator to continue his increasingly Quixotic pursuit of the nomination. Sanders has used the tumult surrounding the pandemic to champion his prized Medicare for All policy goal in an effort to calm voters during the pandemic. But on a controversial day of voting on March 17 amid health safety concerns in Illinois, Arizona and Florida, Sanders failed to win any contests.

In the Wisconsin primary on Tuesday—the lone April contest not to be rescheduled in the name of public health, despite numerous warnings from local officials—Sanders faced another likely blowout, as Democratic voters sought to wrap up the nomination contest and remove at least one variable from a moment in American history defined by uncertainty.

The 78-year-old senator resisted the idea of earlier leaving the race after falling behind Biden in most of the March 10 voting contests. He instead committed to facing off with Biden in a one-on-one debate scheduled at that time to be held in Arizona.

When a reporter pressed him during a press conference in Vermont about concerns he might be staying in the race too long as fears about the virus continued on March 13, Sanders said his “long term goal is to win.”

“Under normal circumstances I would not be in Burlington today. I would be probably in Ohio, Florida or another state where a primary is coming up,” Sanders said. “But we’ve decided not to do, under the advice of public health officials, not to do rallies and that's the right decision.”

Following the trio of double-digit losses to Biden in Arizona, Florida and Illinois, the Vermont senator had expressed frustration with the focus on the future of his campaign, telling reporters on Capitol Hill that he was “dealing with a fucking global crisis.”

After falling short of the Democratic nomination in 2016, Sanders and his supporters reveled in the idea that the Vermont independent’s campaign had deeply influenced the policy platforms of other 2020 candidates. Medicare for All became a type of litmus test for the others in the field.

And while dealing with health-care hamstrung the campaigns of Sens. Kamala Harris (D-CA) and Elizabeth Warren (D-MA), Sanders’ supporters routinely praised him for his consistency on the issue.

Sanders’ candidacy was almost derailed in October when he had a heart attack. But other than talking about changing his routine, the incident did little to hurt the self described democratic socialist’s White House hopes.

A younger generation of progressives led by Rep. Alexandria Ocasio-Cortez (D-NY) actively campaigned for Sanders and popular rock acts like The Strokes and Vampire Weekend played at concerts in support of the liberal powerhouse in the early primary states.

Sanders was able to break from historical precedent and win a repeat victory in the New Hampshire primary before scoring a blowout win in the Nevada caucus that, for a moment, made him the Democrat to beat in the 2020 race.

That frontline position wouldn’t last.

After struggling to gain support from African-American voters during his 2016 run, Sanders again failed to earn their support in 2020, finishing more than 28 percent behind Biden in South Carolina. The win and the endorsement of several former rivals fueled Biden’s near sweep in the Super Tuesday contests on March 3, leaving Sanders at a major delegate deficit.

Sanders inability to grow his support was ultimately his undoing. After his South Carolina loss he railed against “the establishment,” further alienating African American voters who were a key reason behind Biden’s win.

While moderates who dropped out of the race lined up behind Biden ahead of Super Tuesday, Sanders fellow progressive traveller in the race, Warren not didn’t endorse him, or anyone else, when she exited the race last week.

The relationship with Warren, once close, soured over the months of campaigning. She and her staff became frequent targets of Sanders’ loyal and volatile online army.

Sanders also faced continued questions about his strength if he were to become the Democrats candidate in November’s general election. Ahead of South Carolina’s primary, some supporters of Biden and other candidates made it clear they had discomfort with the idea of voting for Sanders given his more liberal views. Others said outright they weren’t sure if they could vote for him.

Appearing on This Week with George Stephanopoulos on March 8, Sanders was pressed about what would happen if he failed to have a path to getting a delegate plurality.

“I’m not a masochist who wants to stay in a race that can’t be won,” Sanders said at the time. “But right now, that’s a little bit premature. Let’s not determine what will happen on Tuesday and what will happen in future.”