Michael Dukakis once proudly proclaimed that he was a card-carrying member of the ACLU. We know how that worked out for him in the 1988 general election.
Fast forward to 2007. Hillary Clinton, with her Senate vote, chose to defend MoveOn.org's defamatory ad aimed at General Petraeus. Petraeus has a 52% favorable rating - a lot higher than the 11% Congress has. The military in general is also something that 69% of people have at least "quite a lot" of confidence in. Compare that to the 14% Congress gets.
Republicans need to hammer this constantly. The Democrats are undercuttign our military while the country is at war. Most people won't stand for that.