It's always hard to know what to make of he-said-she-said allegations. By definition, they are hard to prove. A rumor, a slander, a lie, sticks to one for one's life, like a stench, like a ghost. But, to the contrary, as lawyers will tell you, the best response when accused of something bad, even if you totally did it, is to "deny, deny, deny."

Which brings us to two of the most distasteful characters to have slimed American public life over these past few decades: Donald Trump and Bill Clinton.

A growing number of allegations have been made this week against Trump. First, tape emerged of him bragging about forcefully kissing women and even grabbing them by the genitals without their consent. And now, at least four women have come out and described such abuse from Trump.

In response, Trump is following that cardinal rule: deny, deny, deny.

It was all just locker room talk, he says. Braggadoccio. Bluster. Of course he never did such a thing! And the women who say otherwise are either lying or deluded, bought by sinister interests, or are aliens in disguise. (He may not have actually said that last thing, but he might as well.)

This diverting and denying creates, for Trump, a dangerous paradox. One of the Trump campaign's lines of attack against Hillary Clinton has been to focus on Bill Clinton's alleged sexual depravities. This is fair enough. If Hillary Clinton wins in November, Bill would be, formally or not, the foremost adviser of the president of the United States. It's legitimate to believe that a man who cannot behave appropriately with women will not behave appropriately with political power. And he would indeed wield significant political power in Hillary's White House. This makes him "fair game" as a political target, especially considering what we know about his past.

Bill Clinton has admitted to at least one affair, with Monica Lewinski. And he has been accused of sexual harassment, sexual assault, and even rape, by several women at several points over his adult life. Who knows if these allegations are true.

But as Fox News' Megyn Kelly put it aptly, the Trump campaign is "expecting now for everybody that will be seeing these interviews with these women to not believe them; and one of the things they say in their statement is, 'How dare you reach back decades and look at possible sexual assaults from way before; like, how could it matter?' But the problem is, that's exactly what they are asking people to do when they look at Bill Clinton."

Indeed. By trotting Bill Clinton's accusers out in front of cameras before Sunday's debate, calling them "brave," and insisting their stories be heard, Trump has in a way backed himself into a corner. What makes those women brave and believable, but his own accusers phony? "None of this ever took place," Trump insists, asking voters to take him at his word while at the same time insisting they should not take Bill Clinton at his.

Of course, this paradox plays both ways. The Clinton camp can't really use the new accusations against Trump without appearing just as hypocritical. It's interesting how Clinton supporters think the allegations against Trump are almost certainly true and show he's unfit for office, while also believing that many allegations against Bill Clinton are probably overblown and totally irrelevant to the presidential campaign. How quick we are to dismiss sexual assault allegations when they do not help our own cause.

If nothing else, this is an occasion to look our own partisanship square in the eyes. It's a chance to ask ourselves why we believe one set of accusers and not the other, and whether or not that's acceptable.