I don't think concentrating on the war will work. I think many American's believe the good guys won, bad guy is gone (yeah I know we don't know where). It's not another Vietnam, at least at this point and it's pretty much out of sight out of mind.
The environment will never work. It's to easy for the Repubs to paint anyone concerned about the environment as a wacko. Even many of the conservative "skeptics" on this board feel that way.
Terrorism - That's exactly what Bush will use. He will try to scare everyone into thinking we need to stay the course, we're rooting out the bad guys, raise the alert level at strategic times, etc. and unless another strikes hit's us here at home, he will claim his efforts have been successful and whether it's true or not, there is no way to dispute that claim.
It's the economy stupid - barring wars or tragedy's like 9/11, people really don't give a damn about much more than their own lot in life (not sure if I disagree either). Do we have jobs, can we afford a house, sending the kids to college, that kind of thing. Forget about the deficit, people don't care about that either and it's way to complex to relate it to their lives. Tax cuts for the rich, nope, that won't work. Here in America, where everyone can hope and expect to be rich some day, we want to have those tax breaks waiting for us when our shop comes in.
It's the economy!
Edit to add comment about civil liberties. Nope, that won't work either. It's cynical, but I think people will only care about this issue if it hits them, they really don't care if some guy with a foriegn sounding name is locked up in jail for month w/o a reason. Sad, but, I'm afraid, true