Seth Masket Gregory Koger used Intrade to roughly calculate them. The numbers depress him:
[A]s a citizen I would be really disappointed if the current power alignment continues. The 112th Congress has been abysmal. The Worst. Congress. Ever. During a time when the U.S. has faced immense challenges, the Congress has been essentially paralyzed on major policy problems. Someone ought to pay a retrospective price for the failure. Maybe voters want to blame the Republicans, maybe they want to blame the Democrats, but one party or the other ought to pay for this failure. Prospectively, a continuance of divided government threatens to mean more of the same. If the same players are reelected, that's a mandate for more of the same.
The Dish 