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…

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.