Odds of GOP Taking the Senate - October 10, 2012

By request, I'm updating my calculation of the probability that the GOP will win the Senate.  To refresh your memory, there are 23 Democrat seats and 9 Republican seats up for grabs in November.  The GOP needs to gain a net 4 seats to take outright control of the Senate, or 3 if Romney wins the election.

I am assigning a probability of GOP winning a seat to 16 of the contests, then using the binomial probability formula to determine the odds the GOP will win a specific number of seats.  By summing the odds of all possibilities above a specific threshold we determine the odds of the Senate flipping.  One word of caution, this treats each race as a separate probability event.  In reality, there will be a coattail effect from the presidential race that will tend to lift all of the GOP or Democrat candidates.

Here are my assigned probabilities for each race I am including:

• Nebraska - 100% - This is Ben Nelson's seat and Deb Fisher has this locked up.
• Indiana - 80% - The latest poll here occurred prior to the debate, and the Dem has 40% support.  Pence and Romney are crushing their opponents in this state.
• Nevada - 90% - Heller leads in all but one poll, and all of the most recent ones. One poll gives him a 17 point lead.
• Wisconsin - 50% - Thompson is rebounding.  The most recent poll is PPP giving Baldwin only a 3 point lead.
• Montana - 90% - Rehberg leads in all of the polls, and none have been conducted since the debate.
• Massachusetts - 60% - Brown leads in the most recent poll and has big enthusiasm edge.
• North Dakota - 70% - Dropping the odds here a bit.  Most recent poll gives this a tie, but in the same poll Romney leads by 14.  I don't trust it.
• Virginia - 40% - Kaine is leading in both PPP and Rasmussen.  Given the nature of his campaigning, he clearly has thrown Obama under the bus.  Allen needs to do something here.
• Florida - 35% - Polls are in conflict here.  One calls it a tie, Rasmussen gives Nelson an 11 point lead.  There are a lot of ads running against Nelson right now, more than Obama is running.
• Ohio - 50% - Mandel has tied it up in recent polls and the polls are over sampling Democrats.
• New Mexico - 10% - This one is almost over, the Democrat is leading by 10 in recent polls
• Missouri - 35% - Akin can actually win this.  McCaskill's numbers have been dropping, and she only leads by 6 now.
• Michigan - 10% - This one is likely over.  Stabenow is getting a 20 point lead in the most recent poll.
• Maine - 10% - The Independent will win this race, but he could decide to caucus with the GOP.
• Pennsylvania - 20% - Dropping Hawaii out to include PA.  This race has been tightening.  Casey has the lead but is only polling at 44%.  Not a good place for him.
• Connecticut - 30% - This one is getting harder.  Murphy crossed the 50% mark in the latest Rasmussen.

Given these probabilities we need to win 6 or 7 seats to take control of the Senate.  If Romney wins, we only need to win 6.  If we win 7 of these seats, we take control of the Senate regardless of all other outcomes.

The odds we will win 6 = 87.5%
The odds we will win 7 = 74.1%

Our odds of taking the Senate are excellent.  But they could improve.  If you are looking for candidates to support financially, the best bets are WI, MA, ND, VA, FL, and MO (yeah, Akin, I know, I know).