I don't think it's so much of partisanship as it's just outright distrust of the right.
To be honest, I'll never again trust Republicans. In the beginning I was on the fence because I respected McCain for his tendency to go against his own party, but then he just turned into another one of Bush's cronies.
However, the real reason was the Valerie Plame betrayal. I'm still flabbergasted by the depths of depravity the Republicans have sunk, not only the overstated betrayal of the American ppl with the war, but then to outright leak an undercover CIA agent's name as some sort of payback, compounded by the fact that there was hardly any punishment handed out makes me physically ill. If I were in such a party, I would denounce them and sever any ties to said party...yet no one did anything. There should've been protests and molotov cocktails tossed at them when Bush commuted Scooter Libby's sentence, but no one did anything because the corruption runs so deep with them these days.
Democrats have their faults as well but the Republican party really needs to reinvent itself.