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Democrats' Edge in House Popular Vote Would Have Increased if All Seats Had Been Contested

by Devin McCarthy // Published January 9, 2013

In the aftermath of the 2012 House elections, many political observers noticed an uncomfortable fact: Democratic House candidates won more raw popular votes than Republicans, but Republicans won 33 more House seats than Democrats. A new FairVote analysis suggests that if both parties had run candidates in all 435 congressional districts, the Democratic margin of victory - and the amount of distortion in the election results - would have been even greater than the partisan skew indicated by the raw vote totals.

There were 45 districts in which either Republicans or Democrats did not field a candidate on November 6, including districts with intra-party races in California and Louisiana. We projected likely vote totals for each party in those districts had both parties run candidates. The projected party vote totals for a district were made using the partisanship of the district (based on President Barack Obama's 2008 vote percentage in the district), the average voter turnout in contested districts in that district's state*, and the "incumbency bump" that the incumbent candidate would likely have received (based on the average nationwide incumbency bump for each party). The actual vote totals from those districts were ignored, because they were likely distorted due to the lack of major party opposition.

This method projects that Democrats would have won about 6.5 million votes in the uncontested seats had they been contested, while Republicans would have won about 5.8 million votes in those seats. When added to the raw vote totals from contested districts, those numbers would have given Democratic house candidates overall 62.3 million votes compared to 59.4 million votes for Republicans. That's a two-party split of 51.2% to 48.8% in favor of Democrats.

FairVote has previously estimated, based on how Democratic and Republican candidates performed in open seat races relative to the partisanship of those districts, that there was an underlying voter preference for Democrats of about 52% to 48% in the 2012 election. The projected party split with every district contested fits in well with that analysis. The projected split does not control for the incumbency advantage of Republicans - meaning that even in a year in which many more Repubilcans than Democrats received a boost due to an incumbency bump, Democrats still would have won more than 51% of the overall vote had every district been contested.

The chart below shows four different methods for measuring the overall support for the two parties in House races: the raw popular vote, FairVote's projected popular vote with all districts contested as described above, FairVote's estimate of the support for each party based on the results of open seat races, and a similar estimate derived from the performances of incumbent candidates from each party.

Raw Popular Vote Party Split

Projected Party Split (All Districts Contested)

Party Split Based on Open Seats

Party Split Based on Incumbency Bump

50.5% D - 49.5% R

51.2% D - 48.8% R

51.9% D - 48.1% R

52.0% D - 48.0% R

*When using the national average turnout for a district instead of the average for each state, results were similar: about 6.6 million projected votes for Democrats in uncontested districts and 6.1 million projected votes for Republicans.