You're kidding, right?
Jul 8, 2004 Capitol Hill Blue headline: Republicans Unleash Attack Dogs on Edwards
Maureen Dowd 08-14-2004 - First lady Laura Bush is wildly popular with the American people, but not with New York Times columnist Maureen Dowd, who called her a GOP attack dog" this week for speaking out on stem cell research.
She's been dragged out to be a Republican attack dog on the most contentious issue, stem cell research, . . .
E.J. Dionne, Jr. - Washington Post Writers Group - 04.27.04 headline of story
GOP attack dogs smear Kerry's war record
Nope, I'm not kidding. The use of the word muzzle was to identify the Swifties as Attack Dogs.
If you go to the Johnkerry.com and use the search for attack dogs (meaning Republicans) 250 hits are returned.