Numbers, Facts and Trends Shaping Your World

Democrats Hold Party ID Edge Across Political Battleground


The Democratic Party has substantially widened its margin in party identification over the Republican Party since the last presidential election and has made notable gains in many of this year’s political battleground states.

Nearly four-in-ten voters (38%) identified themselves as Democrats in 2008 surveys by the Pew Research Center; 34% self-identified as independents; and 28% identified themselves as Republicans. These data are based on more than 28,000 interviews conducted this year by the Pew Research Center.

In 2004, the balance of party affiliation was far more closely divided: 35% of voters called themselves Democrats, 33% Republicans, and 32% independents.

The Democratic Party now holds an advantage in party affiliation in several swing states where Barack Obama and John McCain are engaged in intensive last-minute campaigning. In Virginia, the Democratic Party holds a five-point advantage over the GOP (34% to 29%); in 2004, Virginia voters were evenly divided (33% Republican, 32% Democratic). In Ohio, where the Republican Party held a two-point edge in 2004, the Democrats now have a nine-point lead (37% to 28%).

The charts below show that the Democratic Party also has increased its advantage in several “blue” states and cut into the GOP’s lead in some “red” states since the last presidential campaign.

Swing States


Blue States


Red States


Election Year Variability in Party Identification

Previous elections have seen substantial shifts in the balance of partisan affiliation over the course of the election cycle, and 2008 is no exception. With the electorate focusing intently on politics, and new leaders reshaping the images of the parties, fluctuations in party identification are not surprising. In the first half of the 2004 election cycle, Democrats held a substantial advantage in party identification, with 48% of voters either identifying as Democrats or leaning toward the party compared with 43% for the Republicans. But following the conventions, Republican identification ticked upward, and remained at parity with the Democrats through election weekend, contributing to George W. Bush’s successful reelection.


While the Democratic Party entered the 2008 election cycle with an overwhelming advantage in party identification, as in 2004 this lead narrowed substantially following the political conventions. The Democrats’ 51%-to-37% advantage in the primary season narrowed to a slimmer 49%-to-43% advantage in September. But unlike 2004’s post-convention GOP boost which lasted through Election Day, the 2008 boost was short-lived. Interviews with more than five thousand registered voters in October so far have shown the resurgence of the substantial Democratic advantage in party identification seen earlier in the year.

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