Responding to Rob Portman's change of heart on gay marriage after he learned his son is gay, Anil Dash tweets:
Eventually one of these Republican congressmen is going to find out his daughter is a woman, and then we're all set.
Actually, this does make a difference. Remember this chart, showing how members of Congress vote on women's issues?
Sure, the effect is small, but among both Democrats and Republicans, members of Congress tend to vote better on women's issues if they have more daughters. Along the same lines, it's instructive to look at which Republicans in the Senate voted for the Lilly Ledbetter Fair Pay Act. Personal experience makes a difference even here.