For months, establishment and center-left Democrats faced a seemingly intractable problem. Multiple moderate and establishment-friendly candidates were staying in the race, each hoping for the opportunity to try to beat Sen. Bernie Sanders (I-Vt.) in a one-on-one primary fight. But by staying in the race, they were splitting up the moderate lane and allowing Sanders, a progressive outsider, to take the lead. It looked like a classic prisoner’s dilemma: by pursuing their individual goals of stopping Sanders and becoming president, they were helping Sanders on his way to victory.

Prisoners’ dilemmas are notoriously hard to resolve, because they require participants to coordinate and act collectively rather than pursue their narrow self-interests. But in the past week, Democrats seem to have solved theirs. Over the past 72 hours, culminating with Super Tuesday, much of the center-left lane coalesced around Biden, preventing an early and easy knockout win for Sanders. It was a surprising outcome, and one that suggests Democrats have learned some valuable lessons from the bruising interparty contests of recent presidential nominating contests.

Biden’s resurgence started roughly a week ago in South Carolina. After the former vice president finished second in Nevada, African American voters in South Carolina started to rally around Biden, who had always seen the state as a bulwark. House Majority Whip James E. Clyburn, a legendary figure in South Carolina politics, endorsed Biden at precisely the moment when his intervention could do the most good.

After Biden’s blowout win in South Carolina, Democratic leaders across the country started endorsing Biden and two of his chief rivals — Sen. Amy Klobuchar (D-Minn.) and former South Bend, Ind., mayor Pete Buttigieg — dropped out of the race and endorsed him. It’s not clear whether Buttigieg and Klobuchar dropped out for the good of their wing of the party, to ingratiate themselves with a potential future president or simply to spare themselves future losses. But the effect was the same: Voters across the nation continued to shift their support to Biden, and exit polls suggested that many of them decided whom to vote for only in recent days.

Iyanla Fuller, a sophomore at the College of Charleston, says she fears for the future of the country. (The Washington Post)

And Tuesday night, Biden profited from that momentum. He won Southern states with substantial African American populations such as Alabama and North Carolina, and he managed to hold former New York mayor Mike Bloomberg’s vote share down in a wide variety of states across the Southeast. But Biden also won less racially diverse states such as Minnesota and Massachusetts. That’s a very good sign for Biden: It suggests that he’s able to reach into states where Sanders or Sen. Elizabeth Warren (D-Mass.) should perform well, compete and sometimes win. Sanders’s delegate haul will likely grow in the coming days as California, a notoriously slow vote-counting state, tabulates its results and allocates its delegates. But Biden’s showing seems obviously positive.

The former vice president still faces challenges. Bloomberg and Warren remain in the race, and if they don’t drop out in coming days, it’s not yet clear whether they’ll siphon off more votes from Biden or Sanders. Bloomberg has been directly targeting Biden’s African American and moderate base, and Warren has the potential to hold onto some suburbanites who would otherwise choose Biden over Sanders.

None of this means that the Democratic Party has chosen a clear nominee or resolved the deep differences that mark its coalition.

Most importantly, it’s not yet clear how many delegates Sanders will have when Super Tuesday is said and done. Sanders has been banking on California and Texas for delegates, and he may be in better shape once the full totals are in. But even if Sanders ends up with an underwhelming delegate total, he could still stretch the primary out. Democratic rules are proportional, so even if Biden goes on a tear after Super Tuesday, he may not be able to quickly rack up delegates. Sanders could stick around, needling him and attempting to pull the party to the left. It’s exactly what he did to Hillary Clinton in 2016, and he could choose to do the exact same thing to Biden this year, too.

Paul Taylor is a corner store cashier in an impoverished area of Charleston, S.C. He is gay, black and a Democrat. And he may vote for Trump. (The Washington Post)

Still, if the Democratic Party establishment and voters want to stop Sanders, they’ve at least pulled themselves together and finally picked one candidate to fight that battle. That’s more than the Republican Party managed to do in 2016, as Donald Trump consolidated his populist base and racked up the delegates as his primary opponents fought each other. Democratic candidates have spent the whole primary warning about the stakes of the 2020 election. In the past week, the party showed that the commitment to beating Trump wasn’t just talk, even if individual candidates had to sacrifice their ambitions to do it.

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