Some reviewers have been panning the new movie Swing Voter, which stars Kevin Costner as an ignorant and politically apathetic swing voter who ends up casting the decisive vote in a presidential election. I'm sure the movie has its flaws. It does, however, get one thing right: swing voters - on average - tend to be far more ignorant about politics than the rest of the electorate. Like any statistical generalization, this one isn't true in every case. There are some swing voters who know a great deal about politics. They, however, are the exception, not the rule.
I. Explaining the Ignorance of Swing Voters.
As I have discussed in various articles (e.g. here and here), most citizens know little about politics. They are rationally ignorant. Because there is so little chance that your vote will be decisive (less than 1 in 100 million in a presidential election), there's no incentive to acquire political knowledge if your only reason for doing so is to cast a better-informed vote in order to ensure that the "right" candidate wins. Numerous studies find, however, that swing voters - defined as those who are in the ideological center and don't have any strong identification with either party - are among the most ignorant. For example, in my research using questions from the 2000 National Election Study, I found that self-identified "Independent-Independents" could on average correctly answer only 9.5 of 31 basic political knowledge questions, scoring much lower than self-described "strong Democrats" (15.4) and "strong Republicans" (18.7). Many other studies find similar results.
Thus, the voters who know the least are the ones who tend to determine electoral outcomes. Not exactly a comforting thought.
Why do swing voters tend to be so much more ignorant than the rest of the electorate? It's tempting to assume that it's because they are stupid. However, ignorance is not the same thing as stupidity. Even very smart people are inevitably ignorant about a great many things. Indeed, as noted above, for most voters political ignorance is actually quite rational.
Part of the reason why swing voters tend to be ignorant is that they have lower average education levels than committed partisans, and education is correlated with political knowledge. But another important factor is that they tend to be less interested in politics; in most studies, interest in politics is a stronger predictor of political knowledge than any other variable, including education, income, race, gender, etc. Their lack of interest is part of what prevents them from developing strong ideological or partisan commitments in the first place.
As I discuss in this article, the fact that there is little incentive to acquire political information in order to be a better voter suggests that most of those who do acquire such knowledge do so for other reasons. They find politics entertaining or they enjoy "cheering on" their political "team." In the same way, the people who know the most about pro sports tend to be those who enjoy watching games and those with the strongest commitment to their favorite teams. Because swing voters generally don't find politics to be very interesting and by definition have no strong commitment to a party, they have far less incentive to acquire political information than strong partisans do.
II. The Bias of the Partisans.
In noting the ignorance of swing voters, I don't mean to praise the knowledge of committed partisans. Although they tend to know more than the swing voters do, they also tend to be highly biased in their evaluation of the knowledge they acquire, overvaluing information that makes their preferred party look good and dismissing data that cuts the other way (see this article for relevant cites). Like the ignorance of the swing voters, this kind of bias is individually rational behavior. After all, since he too has almost no chance of actually influencing the outcome of an election, the partisan's motive for acquiring political knowledge is less to seek the truth about candidates than to get entertainment value from following politics. And cheering on his party and confirming his prejudices is a big part of the latter for many people.
In the same way, committed sports fans are more interested in rooting for their favorite team and against its rival than in finding out the truth about their relative merits. When I read up on my beloved Red Sox and the rival Yankees, I do it for fun; not because I think I can influence the outcome of Red Sox games or because I want to get at the objective truth about the two teams. "Political fans" tend to be the same way. Sports ignorance and sports fan bias are mostly harmless. Not so with their political counterparts.