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.

The point of all of this is not to suggest that it is impossible for Democrats to retake the House under these current district lines, only that it would be extremely difficult. These data also ignore the historic pattern of the party holding the White House typically losing a lot of House and Senate seats in the second term’s midterm election; it’s happened in five of the past six such “six-year-itch” elections. Of course, the natural tendency for voters to get tired of the president’s party after six years could be offset in 2014 by problems with the Republican brand; so, in that sense, this will be a contest of history versus current circumstances.