Both Dick and Lynne Cheney are criticizing Kerry for mentioning their daughter. This could become a serious flap, and is a great story for the media, but is also an uncomfortable issue for both campaigns. Given the GOP base's feelings about homosexuality (very, very negative), the Bush campaign probably doesn't want to push this too hard. And Kerry surely doesn't want to be seen as either gay-baiting or invading a family's privacy (although Mary is hardly private about her sexuality).
This comes only a day after John Edwards derided Bush as a pom-pom waving cheerleader, so maybe this is some strange new strategy.