As Hillary Clinton embarks on her second campaign for President, she is desperately trying to alter popular perceptions that she is aloof, entitled and out of touch. But there’s one thing about Clinton that she’ll never be able to change: her gender. And, even in this enlightened day and age, that might be what finally blocks her from the White House.

Right now, of course, Clinton is the clear favorite. Her name recognition and fund-raising prowess dwarf those of all the Republican candidates, who will spend much of the next year cutting each other down. By contrast, Clinton probably won’t face a serious challenger for the Democratic nomination. With a full war chest, her backers hope, she’ll trounce her GOP opponent in the general election.

But that’s assuming Americans will vote for a woman for President. Our history — recent history — suggests otherwise. Female candidates are defined by their gender in a way that men never are. And in the public mind, those definitions typically makes the women seem, well, unpresidential.

The first modern female aspirant for the White House was Margaret Chase Smith, the U.S. senator from Maine who was also the first woman elected to that body in her own right. After she announced her candidacy for the Republican nomination in 1964, news reports invariably focused on her “trim” and “white-haired” appearance. They also stressed Smith’s ambition, which was seen as something less than female.

Eight years later, Brooklyn Rep. Shirley Chisholm campaigned for the Democratic nomination, demanding more spending on education and less on defense. But those positions marked her as stereotypically “female” in the eyes of many voters, who wanted a “strong” figure (a man) in the White House. ...