There are two important, interrelated upshots to this. Under the present map, there are 60 Republicans representing districts that were carried by Obama. There will likely be many fewer such Republicans after redistricting is finished. Indeed, under the new map, it may well be impossible for Democrats to win the House without winning McCain districts. In other words, New York 26 is a huge, icing-on-the-cake win under the present map. But Democrats could have to sweep districts that are only a few points more Democratic in 2012 if they want to capture the House. That isn’t an impossible task, but it is a difficult one.
More importantly, it means that the Republicans’ 1.5 percent lead in the generic vote is more substantial than it looks. We may well be heading for a scenario where Democrats win the popular vote, and do so by a not-insignificant amount, but still lose the House. This hasn’t happened since 1942, when Republicans won the popular vote by three points, yet narrowly lost the House. I’m willing to bet that if the House vote is as close as it was in 1996, when Republicans won the national popular vote by 77,000 votes out of 87 million cast, that they’ll keep a comfortable majority.* That’s what the RCP Average is pointing toward right now.