The gender bomb has been dropped on Sen. Bernie Sanders (I-Vt.), thanks to the explosive allegation he told Sen. Elizabeth Warren (D-Mass.) at a private meeting in late 2018 that a woman couldn’t win the presidency in 2020. This might hurt Sanders’s standing with progressive women, but the attack’s fallout is just as likely to harm Warren.

As with many political assaults, the facts are in dispute. Sanders says he did not say a woman could not win, calling the charge “ludicrous” and “a lie.” Warren in turn confirmed the allegation in a statement, saying the topic “came up" at their meeting and that, while she thought a woman could win, “he disagreed.” Thus, Tuesday’s final Democratic debate before the Iowa caucuses will likely be riveted by a classic “he said, she said” exchange.

While no one has claimed responsibility for this act of political sabotage, we can guess someone in Warren’s camp is the most likely culprit. Sanders leads Warren in national and Iowa polls, so his staff has no motive to pick a fight with Warren on the issue of sexism and gender bias. Warren’s campaign, however, clearly does have a motive, as polls show the onetime front-runner losing support to Sanders among men and women. Most people can put two and two together no matter how many times Warren or her staff disclaim any involvement.

Charges such as this have a habit of harming the people who make them. Then-North Carolina Sen. Elizabeth Dole, for example, lobbed a grenade at her Democratic opponent, Kay Hagan, in the final days of their 2008 contest. She released an ad saying Hagan had attended a fundraiser hosted by an adviser to a group called Godless Americans. The ad then recounted that group’s positions and ended with an anonymous female voice saying “there is no God” over Hagan’s picture. This was over the line even in religious North Carolina, and Hagan’s slim lead expanded in the days after the ad was released. She walloped Dole by more than eight points on Election Day.

Warren might discover what many before her have painfully learned: It’s dangerous to be perceived as the attacker in a multi-candidate primary. Time and again, the candidate who tries to create contrasts with another candidate ends up driving voters to a third person who is running a positive campaign. That happened in the 2004 Iowa caucuses, when the Democratic front-runners — former Vermont governor Howard Dean and then-Rep. Richard A. Gephardt (Mo.) — traded blows going into the final days. Voters shifted en masse to then-Sens. John F. Kerry (D-Mass.) and John Edwards (D-N.C.), who each gained more than 20 points in less than three weeks to finish one-two.

The presence of Sen. Amy Klobuchar (D-Minn.) in the race therefore complicates the political calculus. Klobuchar has been slowly raising her own feminist flag in recent months, gaining attention when she commented in one debate that she raised $17,000 in her first campaign from ex-boyfriends. Democratic women who are looking for a strong, electable female could easily look at the Warren-Sanders food fight and decide that a woman can and should win, just not Warren. Klobuchar’s team must be thanking its lucky stars to have been handed this gift on the eve of the crucial debate.

Sanders shouldn’t think he is home free just yet. He will need to defend himself carefully Tuesday night, avoiding any heated exchanges that could raise their own questions about his temperament and fitness for office. Just as sometimes the coverup is more harmful than the crime, sometimes in politics the reaction is more damaging than the charge. Sanders draws strength from his hot and intense manner, but that habit could hurt him greatly Tuesday night if he indulges in his sense that he has been unfairly maligned.

Former vice president Joe Biden will also have to tread carefully even though he is not directly involved. Biden has his own history of being too touchy-feely toward women in public. Don’t be surprised if this comes up Tuesday night, pushing a man widely considered a human gaffe machine into an unwanted impromptu exchange.

It is ironic that a party that increasingly prides itself for being the voice of nonwhites, women and sexual minorities has two straight, white men as its front-runners. This desperate gambit might not help Warren, but it has the potential to completely upend the race as the candidates enter the final turn.

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