Limits of the Party Identification Variable

As you finish your papers, ponder the limits of party identification in polling. An individual's party affiliation is a good predictor of her or his vote, but statewide party identification sometimes produces anomalies. Stuart Rothenberg explains:

Gallup found self-identification in South Carolina at 42.8 percent Democratic and 42.3 percent Republican, for a Democratic advantage of one-half of 1 point. That makes the Palmetto State “competitive” according to Gallup’s system of classification.

That may indeed be the way people in South Carolina identify themselves by party, but it isn’t the way they vote. The state has two GOP Senators, a Republican governor and four Republican Congressmen, compared with two Democrats. The last Democratic nominee for president to carry the state was Jimmy Carter in 1976 (before most of the South had realigned), and in 2008, Republicans won large majorities in both chambers of the South Carolina Legislature.

The moral is that party identification may be a lagging indicator. In South Carolina, many older white voters may still think of themselves as Democrats even though they often vote Republican. So in judging a state's leanings, look at election results, not just poll data.