When Gerry Meets Dummy in Illinois

The Illinois congressional redistricting maps are expected to be finalized in the next week and Democrats are licking their chops expecting big gains. They have to be careful, however, as a district they may think is Democratic might not actually be. Republicans won 7 congressional seats in 2008, the year Obama was taking 63.8% of the vote in Illinois. Of those 7, Obama won 4 of them.

Six of those were won by incumbent Republicans, while the 7th was an open seat. Democrats took one open Republican seat. In fact, Democrats didn't beat an incumbent Republican in either 2006 or 2008, while Republicans knocked off four Democratic incumbents in 2010.

The chart above shows that Obama only beat the average Illinois Democrat by 2 points. The problem with that is that it includes districts where the incumbent democrat won over 85% of the vote four times. It'd be difficult for Obama to beat those. It also includes an estimate for what Phil Hare would've gotten had he not been unopposed.

If we exclude districts Democrats hold now, and ones Republicans likely won't compete in, the average margin a Republican did better than McCain did was 6.4%. If we further narrow it down and eliminate the three districts Republicans won in 2010 but didn't win in 2008. This includes CD-17, where they didn't even offer a candidate. The average Republican did 12.7% better than McCain did, with the worst of the eight doing 9.8% better. On average McCain got 47.2% in their districts, while they got 59.9%.

If an incumbent Republican does at least 9.8% better than the Republican nominee, then it's likely that any district the GOP currently holds and Obama gets less than 59.9% is one the Republicans will win. Peter Roskam is in a suburban Chicago district that the Democrats would like to get. Since he finished 14.2% ahead of McCain he might be favored in any district Obama got 64% or less of the votes.

IMO, Republican incumbents should be safe in 2012 in any district that's drawn that Obama got 56% or less, feel confident in districts he got 57-59% and be competitive in districts Obama got 60%-64%. If the Democrats make a lot of districts where Obama won 58% of the vote, they will likely lose them. People will split their tickets in Illinois and vote for the congressional candidate they like who is a Republican and the President from their home state.