The Flip-Flop Flap
Noam Scheiber and Jonathan Chait debate whether or not John McCain's flip-flop attacks against Barack Obama will work. Since Chait seems to think these attacks are both effective and unfair, it might be nice for him to spend some time dealing with the unfair flip-flop charges coming from his colleague James Kirchick.
But beyond that, my thought on this question is that conventional wisdom radically misconstrues the nature of the relevant decision-making process. In my model of the electorate, the majority of voters are voting as blind partisans. Of the rest, most are being driven by the macro factors (shitty economy, sick of Bush) or purely by issue salience (vote Republican when I care about national security, vote Democratic when I care about the economy) or other such things. And yet, few people like to say that kind of thing. And this is where the campaign comes in.
The main impact of campaign attacks, I think, is not to actually change anyone's mind but rather to familiarize everyone with the talking points of the side they agree with. In 2000, voters who valued "experience" turned out to favor Al Gore strongly. In the 2008 campaign, I think it's clear that voters who value "experience" will favor John McCain. That's not, however, because there's some coherent bloc of "experience" voters who shifted loyalties -- it's because "experience" was a Democratic talking point in 2000 and it's a Republican talking point in 2008 so people change which candidate attributes they value. In 2004, you could find a lot of Democrats who thought John Kerry military service proved important things about his fitness for office, whereas in 2008 Republicans are more likely to say that about John McCain.
I think that if Obama becomes unpopular and loses the election it'll be because a larger number of voters decide that having a "tough" foreign policy is the most important thing. But if they reach that conclusion, they'll find themselves suddenly agreeing with all manner of other attacks from John McCain's camp. By contrast, if voters continue to be focused on their desire for a sharp break with Bushism, voters will find pretty much anything Obama throws at McCain persuasive.