The height differential in this photo illustrates one more barrier female candidates face: From our worship of athletes to our habit of electing the taller presidential candidate, we tend to think of "leaders" as big, physically imposing people. Witness the endless negotiations on podium height, standing vs. sitting, and who walks over to who in presidential debates.

But leaders come in all sizes: I remember with a bittersweet tear in my eye a photo of Bill Bradley and Paul Wellstone campaigning together.