Hillary Clinton is not a perfect presidential candidate for the Democratic Party. She accepts too much money from Wall Street. She has a weird history on gay rights. She’s kind of a hawk. There’s the email thing. These factors, among others, have driven lots of Democrats into the waiting arms of Bernie Sanders. If you bring up the fact that it might be nice to finally have a female president, Sanderistas will quickly retort that it’s sexist to vote on account of gender, and that they’d happily vote for a female presidential candidate over a male one. Just not Hillary Clinton.

I have no doubt that some Sanders supporters legitimately favor his policies over Clinton’s, and that they might vote for a woman with Sanders’ ideology. But my strong suspicion is that, in any nominating race featuring a female candidate, there will always be a Bernie Sanders—a male alternative whose gender allows him to do everything his female opponent cannot. And the key question for Democratic voters, post-Iowa, is whether they will allow themselves to be so wooed by Sanders’ gendered appeal that they abandon the woman who seemed poised to make history.

Before this election cycle, the clearest example of the male-alternative phenomenon was the 2008 Democratic primary battle. Early in the race, Clinton seemed to be a clear favorite. She positioned herself as practical, hard-nosed, and shrewd—qualities likely designed to dispel gross stereotypes about the ostensible weakness of her gender. Predictably, it freaked people out.

Clinton tried to reverse course, to show her soft side, but it was too late. Sen. Barack Obama framed himself as Clinton’s emotional antipode: an idealistic, optimistic, ebullient dreamer. The subtext of his message was that there will be time to elect a female president later; now is the time to elect me.

Obama’s strategy was probably not borne out of canny sexism; most misogynistic dog whistles emerged from the right-wing press, not his campaign. Still, Clinton was boxed in completely: If she stuck with her tough-minded pragmatism, she would continue to be depicted as an unlikeable shrew. (Fox News: “When Barack Obama speaks, men hear ‘Take off for the future!’ When Hillary Clinton speaks, men hear ‘Take out the garbage!’ ”) If she campaigned on her emotions like Obama, she would be mocked mercilessly as weak (at best) or manipulative (at worst) by her foes in the press. Clinton lost the primary for many reasons, but I’m convinced that there was a gendered element to her defeat; too many voters bought into the image of her as a cold, calculating virago. And although Obama has been a staunch defender of women’s rights, girls still grow up in this country wondering why, if women can really do anything they want, Americans have never deemed a woman capable of being president.

This time around, Clinton changed her tune. Aware that her tough demeanor put off some voters, she presented herself as a positive, cheerful pragmatist. “A progressive who likes to get things done.” A warrior for the middle class—but a pleasant and amiable one, not a calculating establishment politician. This, too, made Clinton an easy target for her opponents in the media. By attempting to seem genuine, the theory went, Clinton proved herself to be a fraud: Anyone who had to try to seem genuine could not possibly be genuine. On the far left, a hypothesis emerged that Hillary was only pretending to seem affable and populist in order to obscure her deep Wall Street ties.

In stepped Sanders: Brash, no-nonsense, straight-talking, uncompromisingly liberal. (Or so he liked to claim: In actuality, Sanders has a spotty record on gay rights and a terrible record on guns.) Oh, and he’s a man. Democrats flocked to him as a more progressive alternative to Clinton, despite the fact that his legislative strategy hinges on a “political revolution” that will apparently involve Republicans instantly dematerializing upon his inauguration. He and Clinton have mostly minor policy disputes, but Sanders is heralded as a true progressive, even though his most liberal proposals are politically dead in the water. Still, Sanders’ angry populist demagogue shtick goes over extraordinarily well with young liberals, especially white ones, who are weary of horse-trading incremental change. As Rebecca Traister recently noted, Clinton would be committing political suicide if she were equally loud and indignant and unkempt and fiery. “No one likes a woman who yells loudly about revolution,” Traister wrote. Hillary is, once again, boxed in by gender politics—and once again, a male alternative has swept in to claim her prize.

There is, of course, an obvious rejoinder to my theory: This could just be a Clinton issue. There are millions of Democrats who deeply dislike Clinton for nongendered reasons—who fear her baggage, her eagerness to compromise, her corporate pedigree. These voters might embrace any other candidate, male or female. Traister doesn’t think that’s right: “It’s not just this woman,” she insists; it’s a “paradigm” that forces women to be “organizational workhorses behind social movements” and allows men to be “gut-ripping orators.” Obama, Sanders, whoever—the male candidate, Traister believes, is always allowed to be more passionate, more rabble-rousing, more fun (and thus more electable) than the female one.

Perhaps. The obvious problem is that we have so little data: Only twice in American history has a woman been a serious presidential contender; both times, that woman was Hillary Clinton. The paucity of data itself speaks volumes. Why don’t we have other women to compare Clinton to? Could it be because most women, facing the challenges that Clinton faces now, are not allowed to rise to the top tier of candidates? Is it because any woman powerful enough to run for president will quickly become undone by the image of power she projects? Are women simply hesitant to put themselves through the indignities that Clinton has suffered? I don’t know the answers, but the questions worry me. They suggest that no female candidate, however qualified, can ever be strong enough to fight back a challenge from a Sanders-type male rival. In other words, in any given race featuring a female candidate, there will always be a Bernie Sanders who can do what she can’t do and say what she can’t say. And if there will always be a Bernie Sanders, then there may never be a female president of the United States.

Read more Slate coverage of the Democratic primary.