Though Comey’s judgment about things that affect political campaigns is not good, I think he’s sincere in wanting Democrats to win in November. But his worry is misplaced. Partly, this is because Democrats are not, in fact, rushing to the socialist left in great numbers. “Overall, it's not really true that the insurgent leftist candidates, like the candidates who are affiliated with the D.S.A. or Bernie Sanders’s group, are doing all that well,” said Alan Abramowitz, a political scientist at Emory University who specializes in partisan polarization. With many of this year’s primary races completed, Crowley is the only Democratic congressional incumbent so far to lose to a challenger from his left. Ocasio-Cortez is a bright, exciting new figure in the Democratic Party, but she doesn’t define it.

And even people like Comey — center-right figures who are momentarily allied with Democrats because they abhor Donald Trump — should be cheered by the energy that Ocasio-Cortez and others like her are creating. In the midterms, passion is likely to matter more than appeals to an ever-shrinking pool of swing voters, who at any rate tend to be idiosyncratic economic populists rather than the judicious centrists of Beltway imagination.

I’m not wholly unsympathetic to people of good faith who want Democrats to win in November, but who fear that America is more conservative than left-wing activists like to believe. I grew up at a time when Democrats were deeply afraid of liberal overreach. For many of the people who taught me about politics, the debacle of George McGovern’s 1972 rout was formative. Its lessons were reinforced by the overwhelming defeat of Michael Dukakis, who was painted as soft on crime and mocked by George H.W. Bush for being a “card-carrying member of the A.C.L.U.,” as if concern for civil liberties were shameful. I wasn’t old enough to vote when Bill Clinton was first elected, but I remember what a relief it was when he broke the Republicans’ 12-year stranglehold on the White House, and how necessary and worthwhile his compromises seemed.