U.S. Senate Race

03 Nov 2008

Senate Democrats* Senate Republicans
100.0% probability of a majority 0.0% probability of a majority
Mean of 59 seats Mean of 41 seats

Electoral College Map

Washington Oregon Idaho Montana Wyoming North Dakota South Dakota Minnesota Wisconsin Iowa Illinios Indiana Colorado Utah New Mexico Texas Nebraska Oklahoma Kansas Nevada California Arizona Missouri Arkansas Louisiana Mississippi Alabama Tennessee Georgia Kentucky Ohio Michigan Pennsylvania West Virginia Virginia Hawaii Alaska North Carolina South Carolina Florida New York Vermont New Hampshire Maine Massachusetts Rhode Island Connecticut New Jersey Delaware Maryland District of Columbia

Yesterday’s analysis showed control of the Senate squarely in the hands of the Democrats by 58.7 seats (on average) 41.3 seats for the Republicans.

There were twelve new polls in seven states released today. In aggregate, they very slightly tilt in favor of the Republicans.

After 100,000 simulated elections, Democrats control the senate 100,000 times, there were 0 ties), and Republicans control the Senate 0 times. Democrats have a 100.0% probability of controlling the Senate and Republicans have a 0.0% probability of controlling the Senate.

Here is the distribution of Senate seats from the simulations:*

It looks like there will be 58 or 59 seats in the hands of the Democrats—59 is slightly more probable.

This graphs shows the probability of at least each number of seats controlled by the Democrats:*

  • 100000 simulations: Democrats control the Senate 100.0%, Republicans control the Senate 0.0%.
  • Average ( SE) seats for Democrats: 58.6 ( 0.6)
  • Average (SE) seats for Republicans: 41.4 ( 0.6)
  • Median (95% CI) seats for Democrats: 59 (58, 60)
  • Median (95% CI) seats for Republicans: 41 (40, 42)

Expected outcomes from the simulations:

  • Democratic seats w/no election: 37
  • Independent seats w/no election: two
  • Republican seats w/no election: 26
  • Contested Democratic seats likely to remain Democratic: 12
  • Contested Republican seats likely to remain Republican: 16
  • Contested Democratic seats likely to switch: none
  • Contested Republican seats likely to switch: seven

This table shows the number of Senate seats controlled for different criteria for the probability of winning a state:* Safe>0.9999, Strong>90%, Leans>60%, Weak>50%

Threshold Safe + Strong + Leans + Weak
Safe Democrat 54
Strong Democrat 4 58
Leans Democrat 0 0 58
Weak Democrat 0 0 0 58
Weak Republican 1 1 1 42
Leans Republican 0 0 41
Strong Republican 7 41
Safe Republican 34

This table summarizes the results by state. Click on the poll number to see the individual polls included for a state.

# Sample Percent Percent Democrat Republican
State @ polls size Democrat Republican % wins % wins
Alabama 1 630 33.0 67.0 0.0 100.0
Alaska 3 1409 57.1 42.9 100.0 0.0
Arkansas 0 0 (100) (0)
Colorado 4 3549 57.2 42.8 100.0 0.0
Delaware 1 644 67.4 32.6 100.0 0.0
Georgia 7 4798 48.0 52.0 2.7 97.3
Idaho 1& 392 42.3 57.7 1.3 98.7
Illinois 1& 744 63.4 36.6 100.0 0.0
Iowa 3 1911 63.2 36.8 100.0 0.0
Kansas 1 583 35.5 64.5 0.0 100.0
Kentucky 5 3079 47.1 52.9 1.2 98.8
Louisiana 1 393 59.0 41.0 99.4 0.6
Maine 2 1150 42.4 57.6 0.0 100.0
Massachusetts 1 606 63.0 37.0 100.0 0.0
Michigan 3 3061 61.6 38.4 100.0 0.0
Minnesota 7 3941 50.0 50.0 48.9 51.1
Mississippi 2 1055 45.4 54.6 1.9 98.1
Mississippi 1& 455 35.2 64.8 0.0 100.0
Montana 1 2652 73.2 26.8 100.0 0.0
Nebraska 1& 450 42.2 57.8 1.0 99.0
New Hampshire 10 5804 54.9 45.1 100.0 0.0
New Jersey 5 3217 59.1 40.9 100.0 0.0
New Mexico 4 3232 58.5 41.5 100.0 0.0
North Carolina 11 8100 52.9 47.1 100.0 0.0
Oklahoma 2 1211 42.0 58.0 0.0 100.0
Oregon 6 4026 53.6 46.4 99.9 0.1
Rhode Island 1& 460 78.3 21.7 100.0 0.0
South Carolina 1 634 40.2 59.8 0.0 100.0
South Dakota 1& 552 62.0 38.0 100.0 0.0
Tennessee 1& 576 38.5 61.5 0.0 100.0
Texas 1& 475 42.1 57.9 0.7 99.3
Virginia 6 4623 64.2 35.8 100.0 0.0
West Virginia 1 2085 59.2 40.8 100.0 0.0
Wyoming 1 485 36.1 63.9 0.0 100.0
Wyoming 1 475 36.8 63.2 0.0 100.0

@ Current party in office
& An older poll was used (i.e. no recent polls exist).
*Analyses assume that independent Senators Sanders and Lieberman continue to caucus with the Democrats.

Details of the methods are given in the FAQ.

The most recent analysis in this and other elections can be found from this page.

(Permanent link to this analysis.)

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