When in 1979 Britain’s voters made Margaret Thatcher prime minister, one conclusion that did not trip instantly to everyone’s lips was that she won because she was a woman. Only in America do we have checklists of political and moral self-satisfaction.

Today, two women bid to become “America’s first woman president”—Democrat Hillary Clinton and Republican Carly Fiorina. Only one is running on this as reason alone to vote for her. Announcing her candidacy Saturday at New York’s Roosevelt Island, Hillary Clinton said, “I may...