Democrats face twin struggles as they seek to retake the House majority they lost in 2010. First, the chamber has largely sorted itself out. With 96 percent of Democratic House members representing districts carried by President Obama and 94 percent of Republican House lawmakers representing districts won by Mitt Romney, each party pretty much has the seats God intended. The House simply doesn’t have much elasticity right now. Substantial gains would either require Democrats winning a bunch of Romney districts or Republicans capturing a lot of Obama districts. Given this sorting out and the almost parliamentary-style voting we’re seeing these days, either party would require one heck of a head of steam to pick up a lot of seats from the other side.
But there is a second reason why there is less elasticity in the House. As House Editor David Wasserman of The Cook Political Report points out, notwithstanding all the Democrats in Obama districts and Republicans in Romney districts, the chamber has fewer swing districts altogether. Using The Cook Political Report’s Partisan Voting Index, which ascertains how the presidential voting patterns in each congressional district differ from the national average, we took a look at the 2004 and 2008 presidential-election results in congressional districts (the final PVI incorporating the 2012 results will be available in the next month or so), and compared them with previous years. In 1998, there were 164 swing districts, which we define as a district with a Democratic or Republican PVI of 5 points or less. The swing districts outnumbered the 148 solid “R” districts where Republicans had an edge of more than 5 points, and the 123 solid “D” districts where Democrats had an edge of more than 5 points.
The number of swing districts dropped from 164 in 1998 to 132 by 2000, to 111 in 2002, then to 108 for two elections (2004 and 2006). The 2008 and 2010 cycles both had 103 swing districts, and the total slipped to 99 in the 2012 cycle. Currently, 190 districts have a Republican PVI over 5 points, 28 seats short of a majority; 146 districts have a Democratic PVI over 5 points, 72 seats short of a majority. This PVI analysis points to the inherent presidential voting patterns on a congressional-district level and ignores the strengths and weaknesses of individual candidates.