Friday, June 12, 2009
Barack Obama's victory in the 2008 presidential election represented one of the most dramatic shifts in political power in American history. In terms of both style and substance, the contrast between Obama and George W. Bush is perhaps as great as that between any incoming and outgoing presidents in the modern era. Yet the historic nature of this election should not blind us to the high degree of consistency between the results of the 2008 election and previous elections. New evidence on the results of the 2008 presidential election at the congressional district level reinforces this point.
The following figure displays a scatterplot of the relationship between Barack Obama's share of the vote in 2008 and John Kerry's share of the vote in 2004 in all 435 U.S. House districts. Each point represents a single House district and the diagonal line is the line of equality which is where each district would be located if Obama had received exactly the same vote share as Kerry.
Two things stand out in this figure. First, there was an extraordinarily high degree of continuity between these two elections. The correlation (Pearson's r) between Obama's vote and Kerry's vote is .97, which means that over 94 percent of the variance in the results of the 2008 election can be explained by the results of the 2004 election. Second, the overwhelming majority of the points are above the line of equality, which means that Obama outperformed Kerry almost everywhere. In fact, between 2004 and 2008 the Democratic share of the presidential vote increased in 382 of the nation's 435 House districts and decreased in only 35 while remaining unchanged in 18. Of the 35 districts in which Obama did worse than Kerry, 23 were in the South or Border South including 6 districts in Tennessee and 4 each in Arkansas and Louisiana.
Barack Obama carried 240 House districts including 58 districts that George Bush had carried in 2004. John McCain carried 189 House districts including only one district that John Kerry had carried in 2004. That was John Murtha's district in Pennsylvania which Kerry won by 2 percentage points in 2004 and McCain won by a single percentage point in 2008. There was a striking regional disparity in the results: Obama carried 67 percent of House districts in the North but only 32 percent of House districts in the South and Border South.
There was also a strong relationship between the presidential and House results. Democrats won 208 of 240 House seats in districts carried by Barack Obama while Republicans won 146 of 189 seats in districts carried by John McCain. There was also a clear regional pattern to these results. Twenty-two of the 48 McCain Democrats elected to the House were from the South or Border South. In contrast, only 5 of the 32 Obama Republicans elected to the House were from the South or Border South. As a result, 35 percent of House Democrats from the South and Border South represent districts that were carried by John McCain compared with only 13 percent of House Democrats from the North.
The high degree of continuity between the 2004 and 2008 presidential election results and the strong relationship between the 2008 presidential and House results both reflect one of the most striking features of American politics in the 21st century-the powerful influence of partisanship on elections at all levels. What remains to be seen is whether Democratic gains in 2006 and 2008 reflected a long-term shift in the party loyalties of the electorate or a temporary reaction to events such as the war in Iraq and the recession. The results of the 2010 and 2012 elections may provide an answer to this question.
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