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There are sixteen Senate races this November that look to be possibly competitive.  Twelve seats are held by Democrats, four by Republicans. Sorted by the Intrade likelihood of a Republican win, they are:

• Democratic seats: North Dakota (94%), Arkansas (85%), Indiana (79%), Delaware (75%), Colorado (72%), Nevada (71%), Pennsylvania (59%), Illinois (53%), Wisconsin (39%), California (36%), Washington (35%), New York (30%)
• Republican seats: Kentucky (77%), New Hampshire (75%), Ohio (71%), Missouri (65%)

There’s (at least) two ways we can make a prediction from these numbers. If we assume that each seat goes with the favorite (including Illinois), the GOP picks up eight seats and loses none, leaving Democrats with a 51-49 edge. On the other hand, if we compute the expected value naively, the GOP picks up a little over six seats, leaving Democrats with a 53-47 edge. The problem with the expected value calculation is that the sixteen races aren’t actually independent variables; much of the uncertainty is in common, so we can’t compute the real expected value from these numbers. I think the best way to do it is to award each seat to the favorite, except in toss-ups like Illinois.

Additionally, I think that the Illinois and Wisconsin numbers are low. Illinois Democrats have nominated a horrible candidate. In Wisconsin, I’m assuming that Tommy Thompson will enter the race. If he does, he will be the favorite. A new poll puts Thompson over Feingold by 12. That poll may be iffy, but it’s not out of band from last month’s Rasmussen poll which gave Thompson a 5 point lead over Feingold.

Based on that, and on my belief that things are only going to get worse for the Democrats as the year wears on, I’m going to predict that the GOP picks up nine seats. That’s assuming nothing dramatic happens to change the election’s complexion. If Thompson stays out, you can subtract one GOP seat. If there’s a major international crisis or if unemployment drops dramatically, toss this prediction out entirely.

UPDATE (4/16): Thompson won’t run. That costs Republicans a seat, leaving my prediction at an eight-seat GOP pickup.

This entry was posted on Sunday, March 14th, 2010 at 12:53 pm and is filed under Political. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.