Snatching victory from the jaws of defeat, Joe Biden prevailed on Super Tuesday. Though the final delegate count is yet to come, the overall picture is clear — and can safely be deemed a gut punch for the Bernie Sanders campaign.

In the span of less than forty-eight hours, prospects for the former vice president seemed to transform, while the blowout hoped for and anticipated by Sanders supporters seemed to evaporate almost as suddenly. With the most contests won, Biden has his first ever delegate lead in a presidential race. But, perhaps more importantly, he now has a potentially powerful narrative of momentum on his side. This seems to have been the deciding factor in many of last night’s races, with huge numbers of Biden voters swinging to him late or even on election day itself following his weekend victory in South Carolina. This, more than Biden’s actual delegate lead, may represent the biggest hurdle for Sanders and his movement in the weeks ahead.

The aftermath of South Carolina, which saw centrist candidates and constituencies alike close ranks around Biden as the last viable anti-Sanders option, suggests Biden’s appeal — though perhaps short on substance — is all too real in an electorate where some clearly view him as a safe and familiar vehicle in the upcoming fight against Donald Trump.

The good news for Sanders is that the hitherto crowded field has served to obscure Biden’s many weaknesses, vulnerabilities, and obvious flaws. Save Michael Bloomberg (who today announced his departure from the race following the most expensive campaign flop of all time) Sanders’s message could hardly find a better foil than the former vice president: a longtime friend of big business, proponent of neoliberal trade agreements, and ally of America’s war industry.

With the overall field and forthcoming debates a lot less crowded, Sanders will finally have a clear opportunity to confront Biden on the terrain of policy and ideology — an area in which he may have a distinctive advantage thanks to the resonance of his overall message with the values of a majority of Democratic voters (Medicare For All — his signature policy — continues to poll well across the electoral map, even in states Biden won). While Sanders has long sought to contrast himself with the Democratic establishment, his favorite target has just gotten considerably less abstract.

Biden’s more pedestrian weaknesses as a candidate may also be thrown into sharper relief now that the race has so dramatically narrowed. From strange outbursts at ordinary voters to commands they “vote for someone else” to elaborate stories that turn out to be completely untrue, Biden’s gaffes and impolitic behavior are part of a decades-long pattern that have already seen him blow two previous presidential campaigns.

Though his substantive vulnerabilities are ultimately more consequential, his proclivity for falsehoods, verbal flubs, and simple incoherence only compound the risk of running him against Donald Trump — a reality that cannot be impressed on Democratic voters soon enough. In truth, Sanders is both the better general election candidate and the more electorally viable one: a case his campaign must make aggressively and without qualification in the days and weeks ahead, even as it works to expose the most atrocious aspects of his opponent’s record.

All told, Biden’s emergence as the consensus candidate for America’s liberal establishment has set the stage for a clash between the corporate center and the populist left that could remake the Democratic Party and its electoral coalition for a generation — or render it an irrelevant husk doomed to repeat the mistakes of 2016 in perpetuity.