The question is whether any or all will try to claim the mantle of Sanders and lead the party on a giddy march to the left. Some Democrats seem to think that if pandering to base voters is good enough for Republicans, it’s good enough for them.

In reality, it would be unwise as policy and as politics. The litmus test may be Sanders’ single-payer health plan, which would combine extravagance with uncertainty and disruption. It would also let Republicans change the subject from their unpopular efforts to dismantle Obamacare.

Democrats have done well in recent presidential races, winning the popular vote in six of the past seven elections. What all their nominees had in common was being close to the center of the party. Bill Clinton, Al Gore, and Hillary Clinton were essentially pragmatists. Conservative blogger Andrew Sullivan characterized Barack Obama as “a de facto moderate Republican”—a description Obama more or less accepted.