From Peggy Noonan:

Hillary doesn’t have to prove her guy chops. She doesn’t have to prove she’s a man, she has to prove she’s a woman. No one in America thinks she’s a woman. They think she’s a tough little termagant in a pantsuit. They think she’s something between an android and a female impersonator. She is not perceived as a big warm mommy trying to resist her constant impulse to sneak you candy. They think she has to resist her constant impulse to hit you with a bat.