The "Catholic Vote" is Tautological

A new survey from Gallup shows an even split among Catholic voters—46 percent support President Obama, and 46 percent support Mitt Romney. If you disaggregate by race, the picture looks very different; only 38 percent of non-Hispanic Catholics support Obama, compared to 70 percent of their Hispanic counterparts. Among white Catholics, if you break the numbers down by religiosity, the most religious and moderately religious support Romney, while the nonreligious support Obama.

This data has led the Washington Post to declare that Catholics are the “bellweather” swing vote for the 2012 election. Here’s Chris Cillizza and Rachel Weiner:

[I]n the last two presidential contests the Catholic vote has tracked almost exactly with the popular vote. In 2008, President Obama carried Catholics by nine points and beat Arizona Sen. John McCain (R) by seven points nationally. Four years earlier, Bush won the Catholic vote by five points and beat Massachusetts Sen. John Kerry (D) by three points nationwide.[…]

The eight presidential elections reveal how up for grabs Catholics truly. The Republican nominee has carried Catholics four times, the Democratic nominee has carried Catholics four times. With the exception of Bill Clinton, who beat Bob Dole among Catholics by 16 points, no candidate has had a winning margin among that group.

The problem with this is that, when you consider the data on its own terms, you find that Catholic voters are almost identical to all other Americans in their voting behavior. To win the Catholic vote is to win outright, because—as Cillizza and Weiner point out—the Catholic vote is nearly indistinguishable from the overall two-party vote.

This makes perfect sense; the Gallup data shows that the disagreggated Catholic vote breaks down along familiar racial and religious lines—-with the exception of the most religious voters, it’s not Catholicism that’s driving the behavior of Catholics; it’s race, gender, and ideology.

True swing demographics—like independents, white women, and the moderately religious—do not track with the overall two-party vote. By contrast, if you were to take a random sample of Catholics and compare their preferences to a random sample of all voters, the results would probably be close, if not indistinguishable.

Catholics are too diverse and too close to the median voter for the Catholic vote to provide any useful information about broader performance. In other words, the “Catholic vote” is tautological—winning Catholics means winning the general public, and vice versa.