Bernie Sanders

Last month, as accusations that Graham Platner of Maine had demeaned and threatened women consumed his Senate campaign, his left-wing allies closed ranks around him.

Representative Ro Khanna of California posted a video on social media sitting alongside Mr. Platner on a floating dock discussing “transformational politics.” Senator Bernie Sanders of Vermont said Mr. Platner had “gotten his life together” despite his troubling past.

“There are no saints in the United States Senate,” Mr. Sanders said at the time.

This week, after one of those women accused Mr. Platner of rape, those same politicians withdrew their support, and Mr. Platner, who denied the accusation, announced Wednesday that he was suspending his campaign. The collapse of his meteoric candidacy has turned what had been a triumph for progressives into a moment of political crisis.

It has also set off a broader debate among Democrats around the country about the movement that Mr. Sanders leads: Is its embrace of a blunt and brawny populism too dismissive of women — and too forgiving of male misconduct? The question is not new, but it has grown more urgent this year, when the party has elevated inexperienced and authentic candidates, such as the flannel-clad Mr. Platner, to stir average Americans.

“What I have an issue with is not the policies,” said Shannon Watts, the founder of Moms Demand Action, a gun-safety group, who was castigated online for not backing Mr. Platner. “It’s the lack of character. It’s being bombastic. It’s that you’re polarizing and alienating and, frankly, it’s also being denigrating toward women.”

Perhaps no one had as much riding on Mr. Platner’s stunning rise from small-town oyster farmer to candidate for Senate as Mr. Sanders, the best known figure of the political left, who has spent the past year helping catapult progressive newcomers in competitive midterm contests.

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