This week's mainstream coverage of the presidential horse-race has been dominated by a series of polls showing the McCain-Palin ticket with its first stable lead over Obama and Biden. Gallup's tracking poll, USA Today and CBS News all show the Republicans with some kind of lead over the Democratic ticket. But, interestingly, all three polls were also conducted using a higher sampling of Republican voters than in July, raising a question of methodology.
In a year in which Democrats have a lead of 11 million registered voters over Republicans, and have been adding to that advantage through a robust field operation, are pollsters over-sampling Republicans?
Despite a raft of advantages in the electorate for Democrats, in September's first Gallup tracking poll, an equal number of Republicans and Democrats were surveyed (including "leaners") from Sept. 3-5, compared to a 10-point Democratic identification advantage two weeks ago. That partisan makeup of the polling pool resulted in a 5-point lead for McCain in Sept. 5 tracking poll. Meanwhile, the new CBS poll features a 6-point swing in partisan composition toward Republicans, which plays some role in the poll's two-point lead for McCain. Finally, the latest USA Today poll, which claims a four-point edge for McCain, was arrived at after a 10-point swing in partisan makeup toward GOP respondents.
Some polling experts say the changing state of party affiliation in the field is slow to be reflected in polls themselves. Democratic pollster Anna Greenberg told the Huffington Post that "when it comes to registration and turnout, the polls often do a very bad job of taking those [factors] into account," because newly registered voters aren't in the voter files used by firms that survey public opinion. "You could make the argument they are under-representing new registrants," she said, which would mean that the Democrats new edge would not be taken into account.
Monday's USA Today poll had a 48-47 split between Democrats and Republicans surveyed. That represents a nearly 10 point shift in party identification toward Republicans since USA Today's July polling. When asked for comment, USA Today polling editor Jim Norman wrote that "it's possible" that their latest sample includes too many Republicans. Though he added, "it's also possible that we have too many Democrats," because "there's always the chance of an over- or under-representation" in polls.
Still, Norman admitted that the GOP identification in the latest survey has spiked. "The party ID in our most recent poll does show a shift away from what Gallup has been getting in earlier polls, going all the way back to 2005," Norman said. "But previous conventions -- the Republican one in 1988, the Democratic one in 1992, the Democratic one in 2000 -- have also shown shifts in party ID toward the party that had the convention, and those shifts seemed to last, to greater or lesser degrees, though the election. Further, I've been told by Gallup that their tracking poll has shown a similar shift in party ID since the Republican convention. ... I guarantee you we will be watching closely in all of our polls between now and election day to see whether there are further shifts in party ID in either direction."
And it's true. Gallup's own GOP identification (including leaners) has swung six points in the last month, from 42 percent of voters to 48, according to tables provided to the Huffington Post. Meanwhile, solid and leaning Democrats have fallen from 52 to 48 percent of those polled. For political scientists who believe that partisanship is largely stable over time -- and who take note of the advantage in voter registration being experienced by Democrats during the same period -- the newly GOP-heavy poll samples can raise eyebrows.
Emory University political scientist Alan Abramowitz is highly skeptical of the new Gallup, USA Today and CBS polls. About the latter, which showed a statistically insignificant two point lead for McCain, Abramowitz said: "One reason for the dramatic difference between the two recent CBS polls is that the two samples differed fairly dramatically in terms of partisan composition. The first sample was 35.2% Democratic, 26.2 percent Republicans, and 38.6 percent independent. The second sample was 34.9% Democratic, 31.1% Republican, and 34.0% independent. That's a change from a 9 point Democratic advantage to a 3.8 point Democratic advantage. That alone would probably explain about half of the difference in candidate preferences between the two [CBS] polls."
If these polls are improperly reflecting the partisan makeup of the electorate at large, it certainly would go part of the way toward explaining anything beyond the quick "dead cat bounce" after the Republican convention. And if the convergence of polls around a small McCain lead has anything to do with sampling error, it would render any claims about a new equilibrium in the race somewhat moot.
One day before USA Today announced its new poll numbers, it also ran an Associated Press story with the headline "Democrats Post Big Gains In Voter Registration." In that article, the AP noted that, during the primary season, "more than 2 million Democrats [were added] to voter rolls in the 28 states that register voters according to party affiliation. The Republicans have lost nearly 344,000 thousand voters in the same states."
The article proceeded to lay out a variety of statistics that favor Democrats:
Nationwide, there are about 42 million registered Democrats and about 31 million Republicans, according to statistics compiled by The Associated Press.
The Democrats have posted big gains in many competitive states, including Nevada, New Hampshire, Iowa, Colorado and Florida. They have also been targeting historically Republican southern states.
Since 2006, the Democrats have added 167,000 voters in North Carolina, while the Republicans have added 36,000.
Still, that doesn't discount the fact that Republicans have definitely made some gains. As Greenberg notes, "Sarah Palin came out and gave a really good speech. She certainly exceeded the low expectations. And then more people watched McCain's speech than Obama. And now it appears there was a bigger bump for McCain than there was for Obama. ... But there always been more room to grow his vote." Greenberg says the prior lack of enthusiasm among Republicans could have resulted in an inflated rate of survey respondents identifying as independents. "The CBS panels show most of the movement came to McCain from undecided voters, people who were probably holding back from McCain," Greenberg said.
Despite that, Abramowitz simply doesn't think the overall spike in Republican sampling among all three polling firms is an accurate reflection of the electorate. "It's just not likely," he says. Given how important polls can be in the coverage of the race, even a slight assist to McCain during a period in which he is exciting the Republican base could help him solidify a new narrative in the race, regardless of the partisan facts on the ground.