Just how much did Christine O’Donnell’s win hurt the Republicans’ cause? A lot, says forecasting savant Nate Silver of the New York Times. According to Silver’s model, the chances of a Republican Senate takeover have plummeted from 26% to just 15%. Based on current polls, Silver gives O’Donnell just a 6% chance of prevailing. If Mike Castle had won the primary, the odds would have been precisely inverted; he’d have a 94% chance to win.
Assuming O’Donnell loses, Republicans will have to sweep the currently competitive Democrat-held seats and lose none of their own. They look likely to pick up North Dakota, Arkansas, Indiana, and Pennsylvania. But Colorado, Illinois, and Nevada are anybody’s game, and after that, they have to try to win at least three contests currently favoring Democrats. Bottom line: Republicans will make gains—in 100,000 simulations they ended up with an average 47.1 seats—but they probably won’t take over. (Catch up on all things O'Donnell here.)