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.