I've heard some analysts say that McCain's "maverick" theme risks damaging his party by transmitting that while he's a technically a Republican, he's also somehow better or above Republicans. By putting himself above the party, other Republicans down-ticket might suffer from the perceived "dual-attack" on the party's brand.
I've also heard some analysts say that McCain risks damaging his party if he changes the campaign message to something ala "you need me in the white house, because everyone knows that the Dems are going to keep/expand their hold in Congress and you don't want one party running 2 of the 3 branches". Other Republican's running down-ticket might suffer because this broadcasts the message that their demise is a foregone conclusion, even within their own ranks.
What I don't think anyone was expecting was this:
Earlier, a McCain supporter went on Hardball (
http://www.youtube.com/watch?v=eJIQm_7YAUI) spreading the McCain smears about Obama and the Democratic party. The response? Grassroots activist have donated nearly $80,000 in a matter of hours (
http://www.talkingpointsmemo.com/talk/blogs/astral66/2008/10/an-amazing-thing-netroots-acti.php) to a fund to see Senator Michele Bachmann ousted from her position. I think the Republicans are about to get a huge wake up call that people are just about fed up with this brand of politics.
The Constitution makes no mention of political parties and the Framers were very much against them. Many parties have come and gone in our history. It would be interesting indeed to see Republicans sign the death warrant of their own party.