Here’s something to think about for those who say that the only reason Republicans won a majority of House seats last November is favorable redistricting. I agree that Republicans did have a net advantage in redistricting in the 2010 Census cycle, but not an overwhelming one: Republican advantages in Florida, Michigan, North Carolina, Ohio and Pennsylvania were offset to a significant extent by Democratic advantages in Arizona, California and Maryland.
But there’s another factor that gives Republicans an advantage in equal-population districts: clustering. Democratic voters, particularly in the two Obama elections, tend to be clustered in black, Hispanic and gentry liberal neighborhoods in major metropolitan areas and (this makes a difference in state legislative districting but not so much in congressional districting) university towns. Democrats win districts in such areas by huge margins, with upwards of 70% of the vote in many cases. Republican voters are pretty evenly dispersed outside these clusters.
Clustering in big metro areas helps Democrats clinch the electoral votes of several large and medium-sized states: California, Illinois, Massachusetts, New Jersey, New York, with 129 electoral votes. That gives them an advantage in the electoral college, since the only similarly sized states that are safe Republican are Texas and Georgia, with 53 electoral votes. But clustering hurts Democrats in equal population plans.
Proof comes from this “Electoral Reform Map” which divides the United States into 50 equal-population states. The folks who did this want to reduce the power of small states in the Electoral College. They used algorithms in order to draw the states and then smoothed out the boundaries, keeping major metro areas together in one state (or more than one when they have enough population). It’s a pretty neat looking map. And each state would have the same number of electoral votes.
I estimated which of their 50 states had more votes cast for Barack Obama and which had more votes cast for Mitt Romney. My count is Romney 29, Obama 21. So their plan would have produced a Romney presidency. Now obviously the campaign would have been conducted differently if the Electoral College worked that way. But my point remains solid: in an election in which Obvama won the popular vote 51%-47%, a politically neutral division of the nation into 50 equal-population states would have given Romney 58% of the electoral votes and Obama 42%. Equal-population districts work against the Obama Democratic coalition.
This effect was visible as well in elections to the House, which have equal-population districts within each state. Republicans won 234 seats in the House and Democrats 201. Mitt Romney appears to have won (I’m waiting on final counts) 228 House districts and Obama 207.
Interested readers with time on their hands might want to actually calculate the vote in each of these districts, and my estimates may be wrong in a couple of cases. But if I’m anywhere close to right, Romney carried a majority of these equal-population states.