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David Strömberg


WH 2008 Analysis, Nov. 3


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Last updated,

 October 1, 2008

How the probabilities are estimated

 

Compared to the previous analysis on October 29. Obama's chances of winning have risen slightly, from 84 to 87 percent. This is partly due to less remaining uncertainty and partly due to Obama's improved standing in the polls.

 

Probability of winning

Obama McCain
87% 13%

Expected vote share

Obama McCain
53% 47%

Expected number of electoral votes

Obama McCain
325 213

Prob. of winning presidency without popular support

Obama McCain
4% 3%

 Obama has an 87 percent chance of winning the elections, receiving an average vote-share of 53 percent of the two-party vote share and an average 325 electoral votes. The risk that the president elect will not receive a majority of the popular votes is around 7 percent. It is more likely that Obama will be in this position (4 percent) than McCain (3 percent). Consequently, Obama benefits slightly from having the Electoral College system (this increases his chances of winning by 1 percent).  

The Bradley effect

I have estimated the Bradley effect based on 421 elections for House, Senator and Governor, 1998-2006, containing 26 black candidates. The effect is 2-3 percent of the two-party vote share. If there will be a Bradley effect of the same size as the average for the 22 House, Senate and Governor races 1998-2006 for which I have data. The statistics are the following.

Probability of winning

Obama McCain
53% 47%

Expected vote share

Obama McCain
50.0% 50.0%

Expected number of electoral votes

Obama McCain
271 267

 

The table below show the forecasted democratic vote shares (absent the Bradley effect), win percentages and the share of candidate visits that should go to each state, based on opinion polls available November 3.

Forcasted votes, probabilities, by state

State

Forc. Dem.vote

Dem. win probability

Campaign share

OHIO

52.9

78.9

15.7

FLORIDA

50.2

52.1

11.0

PENNSYLVANIA

55.2

92.4

9.9

VIRGINIA

51.1

62.6

8.4

MINNESOTA

53.5

83.4

6.5

COLORADO

52.5

75.2

6.3

MICHIGAN

55.8

94.6

6.0

WISCONSIN

54

86.4

5.8

MISSOURI

49.6

46.3

4.8

IOWA

53.6

83.7

3.6

NEVADA

53.4

82.8

3.0

NEW MEXICO

53.4

82.3

3.0

NEW JERSEY

57

97.4

2.7

NORTH CAROLINA

47.8

27.4

2.5

ARIZONA

47.8

27.3

1.7

WASHINGTON

57.6

98.2

1.6

GEORGIA

46.7

18.4

1.2

MARYLAND

58.4

99

0.9

OREGON

57.6

98.2

0.9

INDIANA

46.4

16

0.8

NEW HAMPSHIRE

56.7

96.8

0.7

ARKANSAS

46.5

17.1

0.5

ILLINOIS

60

99.7

0.5

CALIFORNIA

60.8

99.9

0.4

WEST VIRGINIA

45.7

12

0.3

NORTH DAKOTA

45.6

11.6

0.2

DELAWARE

57.9

98.5

0.2

MAINE

59.4

99.5

0.1

MONTANA

45.3

9.8

0.1

TEXAS

43

2.7

0.1

MISSISSIPPI

44.1

5.5

0.1

CONNECTICUT

61.4

99.9

0.0

TENNESSEE

43.1

2.9

0.0

LOUISIANA

43

2.6

0.0

SOUTH DAKOTA

43.6

3.9

0.0

MASSACHUSETTS

62.9

100

0.0

KENTUCKY

41.7

1.1

0.0

ALABAMA

38.9

0.1

0.0

VERMONT

62.7

100

0.0

SOUTH CAROLINA

40.8

0.5

0.0

UTAH

31.5

0

0.0

IDAHO

31.1

0

0.0

KANSAS

41.7

1.1

0.0

WYOMING

35.3

0

0.0

NEW YORK

65.2

100

0.0

RHODE ISLAND

64.1

100

0.0

ALASKA

41.6

1.1

0.0

DISTRICT OF COLUMBIA

 

100.0

0.0

OKLAHOMA

36.6

0

0.0

NEBRASKA

37.6

0

0.0

HAWAII

62.5

100

0.0