There are more and more independents. By virtue of that very status, it's obvious they don't take orders from anybody. I suspect they're also more likely to do research and think before they vote--and not to be swayed by pathetic stupid smears such as are under discussion.

With Obama as the nominee, the passion on the Democratic side in favor of their candidate is likely to be intense. With Hillary, it would be a pale shadow.

On the Republican side, even if McCain, the strongest candidate, is the nominee, there are a lot of Republicans who don't feel he was strong enough on tax cuts--he opposed the Bush cuts-- (now supports them), are against McCain-Feingold, and especially want to be far more punitive against illegal immigrants than McCain. For all these reasons, and more, the enthusiasm on their side will be tempered--some may well not vote, or vote for a write-in.

The economy is not in good shape, according to the general public perception--people tend to throw out the president's party in that case. The Republicans have been in power since 2000--- (Congress only changed hands ,actually to gridlock, recently)

Iraq is temporarily improving--but at the cost of arming both sides in the potential return of the civil war. This is particularly important, since it's the main reason for McCain's resurrection--and the upward trend could just as easily reverse, especially since "national reconciliation" is painfully slow.

These factors are likely to be more significant than any imagined Rush-Swift Boat etc. campaign.