Political scientists have long recognized that the distribution of party identification in the electorate is one of the most important determinants of the outcomes of elections. And the balance of partisanship is even more important now than in the past because of the high level of party loyalty of American voters in the 21st century. Most recent polls show over 90 percent of Democratic and Republican identifiers who have reached a decision supporting their own party’s nominee. Therefore, the balance of party identification in the electorate will be crucial in determining the outcome of the election.
Although the Democratic advantage in party identification appears to be somewhat smaller now than it was in 2008, most national polls continue to show a fairly sizeable Democratic margin. When we focus only on polls that include the entire voting age population, the Democratic advantage has averaged around 8 points over the past three months.
There is some variation across polls in the size of the Democratic advantage in party identification but every national poll conducted in 2012 has shown a Democratic advantage in party identification in the voting age population. Every one that is except for two—Rasmussen and Gallup. When it comes to measuring the distribution of party identification in the American voting age population, Rasmussen and Gallup stand out from the crowd and they stand out by a wide margin.
The Rasmussen Poll
In 2010, Rasmussen was rated by Nate Silver of fivethirtyeight.com as the most inaccurate and biased major polling organization. This year, Rasmussen continues to produce results that appear to skew in a Republican direction and this is certainly true of Rasmussen’s polling on party identification.
At the beginning of every month, Rasmussen reports its monthly results on the distribution of party identification in the entire American voting age population based on some 15,000 interviews. So far this year, Rasmussen has reported a Republican advantage in party identification every single month from January through July. The Republican advantage has ranged between 1 point and 3 points with an average of 2 points.
Rasmussen is the only polling organization to show a Republican advantage in party identification this year. Although Rasmussen has never explained how they identify likely voters from their initial sample of the voting age population, one can only assume that their presidential preference results among likely voters reflect the Republican skew of their initial sample of voting age adults.
The Gallup Poll
Gallup is the oldest and one of the most respected polling organizations in the world. Unlike Rasmussen, they provide a great deal of information about their sampling methods and share their results and at least some of their data with interested scholars. Gallup also uses what is generally considered state-of-the-art polling methods. They conduct their interviews using live telephone callers and they supplement their landline sample with live calls to cell phones. Currently about 30 percent of Gallup’s interviews are conducted on cell phones.
Despite appearing to follow what would generally be considered best practices in public opinion polling, however, Gallup has been producing results this year from its national tracking poll that differ from those of other polling organizations that use similar methods—results that appear to have a modest but significant Republican skew when it comes to presidential candidate preference. On average, Gallup has shown Barack Obama with a 1 point lead over Mitt Romney among registered voters compared with an average lead of about 4 percentage points for other polling organizations using similar methods.
Gallup’s Republican skew is evident when it comes to party identification as well. In 10 polls this year, Gallup has found an average Democratic advantage in party identification among the voting age population of only 2.1 percentage points. Other polling organizations using similar methods have produced an average Democratic advantage in party identification of 7.8 percentage points since the beginning of 2012. That is based on 28 polls conducted by 7 polling organizations: CBS/New York Times, ABC/Washington Post, Ipsos/Reuters, NBC/Wall Street Journal, Pew, Kaiser and AP/GfK.
It is much harder to explain the Republican skew in Gallup’s polling on party identification than it is to explain it in Rasmussen’s polling. Gallup’s party identification question is different from the questions used by most other polling organizations in that it references “politics as of today” rather than focusing on a longer-term party preference. That may make it somewhat more responsive to current political issues. But that would not explain why Gallup also appears to have a similar Republican skew in its presidential preference polling. Another factor may be the racial composition of Gallup’s sample which may include a slightly smaller proportion of nonwhite respondents than other polls using similar methods although such comparisons are difficult to make because not all polling organizations provide information about the racial composition of their samples.
Whatever the explanation for Gallup’s Republican skew, it is clearly significant. As in the case of the Rasmussen Poll, an initial sample of adults that skews Republican is bound to produce results for registered and likely voters that skew Republican. And because Gallup and Rasmussen are the only polling organizations currently conducting tracking polls and releasing results on a daily basis, their findings have a disproportionate impact on perceptions of the outlook for the 2012 election.