Vermont Sen. Bernie Sanders pledged his campaign would move forward following another series of major losses on Super Tuesday 2.0, in which former Vice President Joe Biden captured by wide margins four of the six states that voted.

“We need to win the voters,” Sanders said during a press conference in Burlington, Vermont, though the far-left senator conceded, “We are losing the debate over electability.”

“I very much look forward to the debate in Arizona with Joe Biden,” he said. The debate is scheduled to take place this Sunday.

On Tuesday, Biden took first place in Idaho, Missouri, Mississippi, and Michigan, carrying every county in the last three states. The Vermont senator’s loss in Michigan was particularly damaging, given the socialist revolutionary’s upset win four years earlier when he narrowly defeated former Secretary of State Hillary Clinton despite being down in the polls by 16 points. Sanders’ loss in the first Midwestern battleground will make it more difficult for Sanders to argue in subsequent contests that he can compete in the critical Rust Belt states that flipped to President Donald Trump in 2016, such as Ohio, which holds its primaries next week.

In the delegate count as of Wednesday afternoon, Biden has expanded his commanding lead over Sanders with 847 delegates to Sanders’ 685 in the race to 1,991, the number required to clinch the nomination in Milwaukee.

Sanders’ collapse Tuesday follows a series of defeats last week, when Biden flexed the strength of his resurgent campaign in the wake of a game-changing victory in South Carolina by capturing 10 of the 16 contests on Super Tuesday, the biggest day of the Democratic primary, including a full sweep of the South. Sanders meanwhile won narrower victories in western states, such as Colorado, Utah, and California, though some news organizations are still saying California is too close to call. Sanders did, however, capture a decisive win in his home state of Vermont.

Throughout February, Sanders had eclipsed Biden as the Democratic front-runner after three straight wins in the early primary states of Iowa, New Hampshire, and Nevada. While Sanders lost the delegate count in the first-in-the-nation Iowa caucuses, the New England progressive still handily won the popular vote by more than 6,000 votes. The Midwestern momentum propelled Sanders to a New Hampshire win and a 26-point victory in Nevada. When the race moved south, however, Biden scored a nearly 30-point win in South Carolina, breathing new life into a sinking campaign. This prompted rival candidates to end their campaign efforts and instead get behind the former vice president to stop Sanders. Three days later on Super Tuesday, Biden delivered with big wins across the country in states where he never even campaigned.

The Vermont senator has tried to resurrect the left-wing movement that propelled his candidacy four years ago. Sanders is running on the same socialist platform — free health care, free education, and free everything — that brought him the support he carried throughout the primaries against Clinton in 2016 and up to this point in 2020.

On Tuesday, however, the road to revolution has become far narrower.