Another contentious House vote; another outcome driven by the partisanship of congressional districts. On Thursday, the House approved a bill that would significantly cut food stamps funding in a 217-210 vote. No Democrats voted for the bill, but 15 Republicans voted against it.

Most of those Republican defectors were from districts where they felt electoral pressure to appeal to Democratic voters. Of the 15 Republican "no" votes, six represent districts that voted for Barack Obama at a higher rate than his national average in 2012. There are only 10 such districts represented by Republicans in the entire country.

An additional four defectors represent districts with Democratic partisanships of at least 47% - that is, districts that voted within three points of Obama's national average. Just 19 Republicans nationwide represent such "balanced" districts, where the possibility of losing in the general election is real enough to influence their voting behavior.

These 15 Republicans were the only ones willing to break ranks and oppose a bill that, regardless of its merits, seems antithetical to the possibility of Congress reaching any compromise on a broader farm bill this fall. They are examples of what FairVote has termed the "bridgebuilders" - Members of Congress with electoral incentives to forge compromises and appeal to all voters in their districts.

Unfortunately, in only a tiny minority of districts are such incentives currently in place. All other Members can vote the party line without electoral consequence, and are strongly encouraged to do so by their parties. For Republicans, that line is becoming increasingly conservative as party leadership responds to the threat of primary challengers from the right. 

FairVote has pointed out this pattern before. In July, we found that both Democrats and Republicans were much more likely to defect on a bill restricting abortion if they represented a district where at least 47% of voters supported the opposite party. Last year, we observed that 16 of the 17 Democratic Members who voted to hold Attorney General Eric Holder in criminal contempt of Congress represeted districts with Republican-favoring partisanships.

This trend has held true for almost all recent House votes that have been decided on primarily party lines. Indeed, earlier this morning, only two Democrats voted with Republicans on a bill that would lead to the shutdown of the government if Obamacare is not defunded. Those Democrats were Jim Matheson and Mike McIntyre, representing, respectively, the first and third most Republican districts of any Democrats in Congress.

Members of Congress will work with the other side when they have an electoral incentive to appeal to the other side's voters. That's why we support fair representation voting for Congress: in addition to electing more moderate candidates, it would give all Members, not just those from the few remaining swing districts, reason to broaden their appeal.