In campaigning for president, Joe Biden faces a difficult dilemma: if he moves left to placate his party’s increasingly socialistic base, he’ll lose the moderate support he needs to challenge Donald Trump. But if he runs as a compromising centrist, enraged party progressives will block his nomination.

Columnist Ross Douthat seems to discern a Biden strategy to thread the needle: shifting left on issues—as he did on federal funds for abortion—while still purveying the moderate image of “good old Uncle Joe,” ready to work with anybody.

The problem is that satisfying progressives requires such radical positions—like racial reparations, forgiving student loans, and banning private health insurance—that middle-of-the-road voters won’t be reassured by an easy-going style. If the election becomes a referendum on a stridently leftist Democratic platform, Republicans should be able to build a big majority in opposition.