It’s true that Biden ought to declare now, but false that he’s running out of time. In fact, his case is stronger than before the debate, which showed that Hillary at her most commanding is still very weak. She’s not going to wipe out the enthusiasm for Sanders. She knows that. Instead, she’s going to do what she’s always done – game the system, grit her teeth, and endure. Voters will fall in line, convinced that Hillary’s inside game is secretly more legitimate than Sanders’ outsider insurgency.

Unless! If Biden runs, suddenly Democrats have a real alternative: not just in an ideological sense, but in a raw political one.

Biden can go toe to toe with Clinton in a way Sanders can’t. He’s got his differences of principle – especially on foreign policy, where Clinton’s weaknesses are the most glaring and controversial. But he’s also the only plausible establishment alternative to Clinton. With apologies to Sanders’ fans, Biden is the only plausible alternative, period. That gives him the authority to draw substantive distinctions with Clinton on the issues Democrats – and Americans – care about most. That’s how he can win his party’s nomination. And it’s how he should.