President Obama told a Columbus, Ohio, crowd Tuesday that Hillary Clinton is "treated differently than just about any other candidate" — and that the reason is sexism.

"I just want to say to the guys out there, I want to be honest. You know, there’s a reason why we haven’t had a woman president before," Obama said.

Obama asked every man who’s voting to "look inside yourself and ask yourself, if you’re having problems with this stuff, how much of it is we’re just not used to it?"

Obama added: "When a guy is ambitious and out in the public arena and working hard, well, that's okay, but when a woman suddenly does it, suddenly you're all like, 'Well, why's she doing that?’"

Obama’s observation is spot-on about how sexism can work in subtle ways. While some research suggests that party matters a lot more than gender when it comes to how people vote, women in power are still at a serious disadvantage when they behave in ways that contradict expected female gender roles.

In one study, Clinton’s support plummeted dramatically among men who were first primed with questions about gender roles before they were asked whom they supported for president.

Calling out sexism this bluntly is a bold but not unexpected move from Obama, our first self-identified feminist president.

But even he isn’t immune to the subtle effects of implicit gender bias against women. When Obama took office, two-thirds of his top aides were men. And once, a group of women in the White House had to come up with a strategy to "amplify" and credit one another’s ideas during meetings, because they were so frequently talked over and ignored by men.