One thing I wonder about is how much do "campaign gaffes" really matter? My guess is that their perceived importance is mostly an illusion. I mean, people point to plenty of examples of campaigns that lost, in large part, "because of" this or that gaffe or damaging random thing dredged out of the record but you never see an example of a campaign that won because it successfully avoided gaffes.
I hypothesize that most people aren't very good at identifying and articulating their real reasons for preferring one candidate over another (how many people say "I'm pretty much a blind partisan" or "all my friends are for Obama and their scorn for Clinton has rubbed off on me even if I think they're overstating it"?) and wind up taking their cues from the press. You're told that the reason to dislike John Kerry is that he's a flip-flopper and so if you dislike John Kerry you cite his flip-flopping.
The 2000 exit polls are interesting in this regard. 13 percent of voters said it was most important to have a president who "understands the issues" and they voted 75-19 for Al Gore. By contrast, 24 percent said it was most important to have a president who's "honest and trustworthy" and they broke 80-15 for Bush. Now I don't believe for a minute that there's a "pro-honesty" voting bloc out there that was alienated by Gore's lies, pitted against a "pro-understanding" bloc that was alienated by Bush being dumb and that that entire 37 percent of the public was genuinely in play and might have swung the other way had Gore been/seemed more honest and Bush been/seemed more intelligent. On the contrary "Bush is dumb and Gore's a liar" was a widespread notion, so people aligned their stated views about presidential qualities with the perceived characteristics of the person they were voting for.
In that same exit poll, 15 percent of the population says that having experience is the most important thing and a stunning eighty-two percent went for Gore. In 2008, however, John McCain is almost certainly going to badly beat Barack Obama among voters who say they put a premium on experience. And yet those people aren't going to be the same people who valued experience in 2000. On the contrary, they're mostly going to be conservatives who voted for Bush in 2000 and dismissed the value of experience. Conversely, liberals who claimed to think experience was crucial in 2000 will have no problem pulling the lever for Obama in 2008.