In the fight over the shutdown, a residual feature of partisan gerrymandering has become unexpectedly important. Andrew Sullivan quotes Kyle Kondik at Larry Sabato’s Crystal Ball:

[I]t’s the House Republicans in marginal districts who could see their ranks decimated, just like the House Democratic moderates whose anti-Obamacare votes couldn’t save them in 2010.

An examination of the MoveOn/PPP data suggests that this burden might fall harder on some Republicans than others. Perhaps surprisingly, a major cause seems to be partisan gerrymandering.

The white symbols show districts in states that I demonstrated in February to be gerrymandered to allow Republicans to eke out many small victories: FL, MI, OH, PA, VA, and WI. The swing in those 12 districts is 14.1+/-8.5 % (mean+/-SD), as opposed to 7.8+/-4.8% for the other 12 districts. (My analysis spreadsheet is here.)

It is a common fallacy to believe that seats gained by partisan gerrymandering are safe seats. In fact, the converse is the case. Gerrymandering achieves a net gain of seats by packing the opposition party into as few districts as possible. North Carolina is a particularly obvious example:

Representatives who benefited from the great partisan gerrymander of 2010 were given enough of an advantage to get into office narrowly. In a district designed to give Republicans a narrow advantage, Republican loyalists are likely to be spread thinly, with the balance of the needed votes being drawn from independents. Some of these independents might be more prone to anger about the current situation. These polls suggest that Republicans in those states might be particularly ripe targets for pressure.

The 12 districts plotted in white are FL-02, FL-10, FL-13, MI-01, MI-07, MI-11, OH-06, OH-14, PA-07, PA-08, VA-02, and WI-07.