Are the polls missing Republican voters?

Voter-file-based data lends credibility to polls showing a lopsided Democratic advantage in other ways. If all the various measures of partisanship — say, Republicans plus-two in Arizona or Democrats plus-two in Florida — are added together across the 94 percent of the nation with a measure of partisanship, Democrats outnumber Republicans by six points, 36 percent to 30 percent. This doesn’t prove that more voters identify as Democrats today, but the Democratic advantage in registration and recent primary participation nonetheless offers evidence consistent with the basic proposition that Democrats outnumber Republicans, and probably significantly.

Using this data, we found that self-identified Democrats outnumbered Republicans by eight percentage points in the Times/Siena national poll (the unrounded figures are Democrats 34.5 percent to 26.4 percent for Republicans). Among those characterized as Democrats based on party registration or primary vote history, 69 percent identified as Democrats in the poll; similarly, 65 percent of those characterized as Republicans identified as Republicans. Those without a party, disproportionately young and nonwhite, split toward Democrats by a narrow margin of 24 percent to 19 percent. At the same time, 6 percent of registered Democrats identified as Republicans, while just 3 percent of registered Republicans now identified as Democrats.