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No, The Polls Aren't Oversampling Democrats

Some allege that the polls oversample Democrats, since they show Democrats outnumbering Republicans by the same margin that they did in 2008, or even more. It does seem hard to imagine that Democrats are regenerating the same support that they received in the midst of a perfect storm, but a closer look reveals that the polls don't show as many Democrats as 2008. 

Consider the “media” polls that have received scrutiny over the last few weeks. With the exception of Fox News surveys that appear to push independent voters, there are fewer Democrats than there were four years ago. So how are Democrats retaining a large advantage in party-ID? Because fewer voters are describing themselves as Republican, as well. Instead, voters are flocking into the “independent” column.

Could this be true? Sure. After all, the Republican Party hasn’t really made a positive case for itself over the past four years, and the Republican nominee hasn’t even really made a case for himself, let alone the party. Put it this way: the Republican Party is not popular, the Republican Congress is not popular, and the Republican nominee is not popular; so how could anyone be especially surprised if a couple points worth of Republican leaners have now decided to characterize themselves as “independents.”

Remember: party-ID can fluctuate without any changes in the political views of voters. After all, voter ideology has remained remarkably stable for decades, despite big swings in party-ID. And it’s not hard to envision why: plenty of voters sit on the fence between a party or independent, and they sway back and forth depending on whether the news, prevailing issues, or major candidates make them feel comfortable about aligning with a political party. I suspect that nearly everyone knows someone who falls into this category (I do). I wouldn't be surprised if several of my Republican-leaning friends are calling themselves independents right now. 

An influx of Republicans into the “independent” column would also explain why Romney remains close among independents despite trailing nationally. It’s also easy to envision how a few independents who lean-Democrat might have switched to the Democratic column following the DNC, which would prevent Obama from gaining among the remaining independent voters who would lean slightly more toward the GOP. If true, Romney's strength with independent voters and the Democratic advantage in party-ID might not be contradictory, but inextricably and coherently linked.

Is there any evidence to support this hypothesis? Yes, although it's not perfect. Some polls ask independent voters whether they lean toward Democrats or Republicans, and recent polls suggest that more independents lean toward Republicans than Democrats. In the Bloomberg survey, the initial Democratic advantage of 6 points dwindles to just 2 points once leaners are added, while the NBC/WSJ poll shows the Democratic advantage narrowing by 2 points after adding leaners. A similar pattern was seen in the Battleground survey, which found that more voters say they vote for a few more Republicans than Democrats. Nonetheless, the balance of evidence seems to be consistent with the possibility that a larger number of Republicans are calling themselves independents than Democrats, at least at the moment. 

Additional support for this hypothesis comes from yesterday's NYT/CBS/Quinnipiac poll of Florida, which showed Obama leading by 9 points. When the poll showed Democrats with a party-ID advantage of 9 points, 36-27, compared to 3 points in 2008, the party-ID police came out in full-force. But the poll also asked whether voters were registered as Democrats or Republicans, and they found Democrats with a 7 point edge, 43-36, compared to their verifiable 4 point edge of 40-36. While that still suggests a somewhat Democratic-leaning sample, notice that fully one quarter of registered Republicans were not willing to identify as Republicans, while only 16 percent of registered Democrats didn't identify as Democrats. Put differently: registered Republicans were 50 percent more likely to call themselves independent than registered Democrats. 

These trends are consistent with the best available data on party-ID. A yearly Pew Research survey tabulating tens of thousands of voters shows that while Republicans haven't gained new adherents over the last four years, Democrats have suffered losses, the number of independent voters have increased, and those independent voters increasingly lean toward Republicans. 

Many Republicans cite Rasmussen as evidence that the GOP has made big gains in voter affiliation over the last four years. They could be right, but they're a startling outlier. The Pew Research survey includes more than ten thousand respondents, which obviates the argument on behalf of Rasmussen's large samples. And almost every poll other than Rasmussen shows Democrats with a persistent advantage among registered voters. Consider, for instance, the party-ID trendline without Rasmussen and PPP/DailyKos/SEIU. 

When the discussion is framed as “how could there be more Democrats than 2008,” it’s easy to see how the “polls are wrong” argument gained currency. But since there are actually fewer Democrats in the polls than 2008, the better question is whether it’s possible for Republicans to have lost self-identified adherents over the last four years, as well. This discussion should be framed by the recognition that the polls are pretty accurate: When assessing whether to “buy” the polls, it’s not a question of whether they match your expectations. The possibility that Republicans are moving into the independent column is an appealing explanation: it contradicts the false assumption that the polls assume a 2008-esque number of Democrats; it reconciles Romney's strength with independent voters and the Democratic-edge in party-ID; and, it happens to be consistent with the polls.