The probability of a Republican House takeover increased slightly over the last week with the mid-point probability estimate advancing by 2% to 72.2%. The number of projected GOP seats in the next Congress was unchanged at 225 seats.
Republican Senate prospects also brightened slightly over the past week. The macro model probability of a Republican Senate advanced by 3.7% to 24.3%, although the micro simulation model projected a takeover probability of only 6%, down from last weeks’ reading of 9%. However, the number of expected seats projected by both the micro and macro models advanced from last weeks’ reading. The micro model’s projection increased to 47.8 seats (up 0.3 seats), while the macro model’s projection improved by 0.5 to 48.7 seats.
The charts below illustrate both the distribution of expected outcomes on both an individual outcome basis and a cumulative basis as generated by the micro simulation model. As you can see clearly both distributions shifted to the right (higher GOP gains) over the past week.
The macro simulation model’s projection of expected Republican seats also shifted to the right (a positive sign for the GOP) over the past week.
This shift should be discouraging for Democrats because these shifts occurred despite declines in Republican probabilities in California, Washington, and Delaware. At present, out of 37 seats on the ballot this November, Democrats post a win probability of greater than 70% in only seven races compared to Republicans posting a win probability of greater than 70% in 22 races.
When we enter October, I will run the models using additional screens in addition to the basic probability model that is presently used in the simulation. While too early to base projections using a narrow set of contested seats, if the narrower screen were to be applied today, Republicans would be expected to hold at least 50 Senate seats in the next election.
As the table below illustrates, despite drops in the probability of victory in a number of states for Republicans, Democrats also saw significant declines in their standing in several states. The data suggests that the chance of Democratic wins in Pennsylvania and Wisconsin are quickly vanishing. For instance, the probability of Democrats holding onto the Wisconsin Senate seat are about equal to Republican prospects to take the New York Senate seat formerly held by Secretary of State Clinton. The difference? In both New York and Wisconsin the trend is in the Republican direction.
| Race | 9/24/2010 | 9/17/2010 | Race | 9/24/2010 | 9/17/2010 |
| Alabama | 100% | 100% | New Hampshire | 79% | 76% |
| Arizona | 100% | 100% | Wisconsin | 74% | 59% |
| Arkansas | 100% | 100% | Florida | 73% | 70% |
| Georgia | 100% | 100% | Colorado | 68% | 66% |
| Idaho | 100% | 100% | Alaska | 67% | 83% |
| Iowa | 100% | 100% | Illinois | 61% | 57% |
| Kansas | 100% | 100% | Nevada | 45% | 45% |
| Louisiana | 100% | 100% | West Virginia | 42% | 38% |
| North Dakota | 100% | 100% | Washington | 35% | 41% |
| Oklahoma | 100% | 100% | New York2 | 33% | 12% |
| South Carolina | 100% | 100% | California | 33% | 44% |
| South Dakota | 100% | 100% | Connecticut | 23% | 23% |
| Utah | 100% | 100% | Delaware | 17% | 25% |
| North Carolina | 92% | 86% | Hawaii | 0% | 0% |
| Indiana | 92% | 87% | Maryland | 0% | 0% |
| Kentucky | 88% | 84% | New York1 | 0% | 0% |
| Ohio | 88% | 89% | Oregon | 0% | 0% |
| Missouri | 84% | 83% | Vermont | 0% | 0% |
| Pennsylvania | 83% | 81% |
Some More Topline Charts
Some Individual Senate Race Charts
