Sunday, August 3, 2008 at 10:58 pm by Darryl
Poll Analysis: Obama v. McCain
| Obama | McCain |
| 98.7% probability of winning | 1.1% probability of winning |
| Mean of 313 electoral votes | Mean of 225 electoral votes |
I’ve changed some of the rules since Friday’s analysis. The changes are documented along with the description of this weekend’s three new polls. In short, the “current poll” window has been reduced from one month to three weeks, and I am now including an additional uncertainty term (uncertainty in p, the probability that a voter goes D or R, that arises because p itself was estimated from a sample).
In any case, Last Friday had Sen. Barack Obama leading Sen. John McCain 333 to 205 electoral votes.
Today, after 100,000 simulated elections, Obama wins 98,681 times (plus he is given the 181 ties), and McCain wins 1,138 times. Obama receives (on average) 313 to McCain’s 225 electoral votes. If an election were held now, we would expect Obama to win with a 98.9% probability. (Most of the difference in electoral votes over last Friday arises from a change to the smaller “current poll” window.) McCain would have a 1.1% probability of winning.
Here is the distribution of electoral votes [FAQ] from the simulations:
- 100000 simulations: Obama wins 98.7%, McCain wins 1.1%.
- Average ( SE) EC votes for Obama: 313.4 (21.2)
- Average (SE) EC votes for McCain: 224.6 (21.2)
- Median (95% CI) EC votes for Obama: 312 (275, 358)
- Median (95% CI) EC votes for McCain: 226 (180, 263)
This table shows the electoral vote total for different criteria for the probability of winning a state: Safe=100%, Strong=90%+, Leans=60%+, Weak=50%+
| Threshold | Safe | + Strong | + Leans | + Weak |
|---|---|---|---|---|
| Safe Obama | 118 | |||
| Strong Obama | 137 | 255 | ||
| Leans Obama | 47 | 47 | 302 | |
| Weak Obama | 20 | 20 | 20 | 322 |
| Weak McCain | 3 | 3 | 3 | 216 |
| Leans McCain | 33 | 33 | 213 | |
| Strong McCain | 173 | 180 | ||
| Safe McCain | 7 |
This table summarizes the results by state. Click on the poll number to see the individual polls included for a state.
| EC | # | Total | % | % | Obama | McCain | ||
|---|---|---|---|---|---|---|---|---|
| State | ‘04 | Votes | polls | Votes | Obama | McCain | % wins | % wins |
| Alabama | 9 | 1* | 457 | 42.7 | 57.3 | 1.5 | 98.5 | |
| Alaska | 3 | 3 | 1467 | 46.1 | 53.9 | 1.5 | 98.5 | |
| Arizona | 10 | 1* | 445 | 44.9 | 55.1 | 6.5 | 93.5 | |
| Arkansas | 6 | 1 | 455 | 42.9 | 57.1 | 1.7 | 98.3 | |
| California | 55 | 2 | 1660 | 57.8 | 42.2 | 100.0 | 0.0 | |
| Colorado | 9 | 3 | 2370 | 50.3 | 49.7 | 57.3 | 42.7 | |
| Connecticut | 7 | 1* | 552 | 62.0 | 38.0 | 100.0 | 0.0 | |
| Delaware | 3 | 1* | 553 | 55.0 | 45.0 | 95.4 | 4.6 | |
| D.C. | 3 | 0 | (100) | (0) | ||||
| Florida | 27 | 4 | 3490 | 49.1 | 50.9 | 21.8 | 78.2 | |
| Georgia | 15 | 2 | 903 | 46.3 | 53.7 | 5.5 | 94.5 | |
| Hawaii | 4 | 1* | 546 | 66.3 | 33.7 | 100.0 | 0.0 | |
| Idaho | 4 | 1 | 450 | 41.1 | 58.9 | 0.4 | 99.6 | |
| Illinois | 21 | 1* | 435 | 57.5 | 42.5 | 98.6 | 1.4 | |
| Indiana | 11 | 1* | 596 | 50.5 | 49.5 | 56.9 | 43.1 | |
| Iowa | 7 | 1* | 430 | 55.8 | 44.2 | 95.8 | 4.2 | |
| Kansas | 6 | 1 | 420 | 38.1 | 61.9 | 0.0 | 100.0 | |
| Kentucky | 8 | 2 | 997 | 44.4 | 55.6 | 0.7 | 99.3 | |
| Louisiana | 9 | 1* | 440 | 38.6 | 61.4 | 0.0 | 100.0 | |
| Maine | 4 | 1 | 450 | 54.4 | 45.6 | 91.2 | 8.8 | |
| Maryland | 10 | 1* | 577 | 57.0 | 43.0 | 99.2 | 0.8 | |
| Massachusetts | 12 | 1* | 430 | 61.6 | 38.4 | 100.0 | 0.0 | |
| Michigan | 17 | 3 | 2727 | 51.9 | 48.1 | 92.2 | 7.8 | |
| Minnesota | 10 | 2 | 1565 | 52.7 | 47.3 | 93.3 | 6.7 | |
| Mississippi | 6 | 2 | 1038 | 44.5 | 55.5 | 0.6 | 99.4 | |
| Missouri | 11 | 1 | 1357 | 47.3 | 52.7 | 8.2 | 91.8 | |
| Montana | 3 | 1 | 658 | 50.0 | 50.0 | 49.5 | 50.5 | |
| Nebraska | 5 | 1 | 455 | 39.6 | 60.4 | 0.1 | 99.9 | |
| Nevada | 5 | 1 | 460 | 51.1 | 48.9 | 63.1 | 36.9 | |
| New Hampshire | 4 | 3 | 1444 | 51.6 | 48.4 | 80.3 | 19.7 | |
| New Jersey | 15 | 1 | 600 | 58.2 | 41.8 | 99.8 | 0.2 | |
| New Mexico | 5 | 1 | 644 | 53.3 | 46.7 | 87.7 | 12.3 | |
| New York | 31 | 1 | 469 | 62.9 | 37.1 | 100.0 | 0.0 | |
| North Carolina | 15 | 5 | 3030 | 48.0 | 52.0 | 5.4 | 94.6 | |
| North Dakota | 3 | 1 | 435 | 48.3 | 51.7 | 30.7 | 69.3 | |
| Ohio | 20 | 3 | 2507 | 51.2 | 48.8 | 79.4 | 20.6 | |
| Oklahoma | 7 | 1 | 600 | 30.0 | 70.0 | 0.0 | 100.0 | |
| Oregon | 7 | 1 | 415 | 55.4 | 44.6 | 94.3 | 5.7 | |
| Pennsylvania | 21 | 3 | 2938 | 54.1 | 45.9 | 100.0 | 0.0 | |
| Rhode Island | 4 | 1* | 430 | 64.0 | 36.0 | 100.0 | 0.0 | |
| South Carolina | 8 | 1 | 465 | 43.0 | 57.0 | 1.7 | 98.3 | |
| South Dakota | 3 | 1* | 420 | 47.6 | 52.4 | 23.9 | 76.1 | |
| Tennessee | 11 | 1* | 435 | 41.4 | 58.6 | 0.5 | 99.5 | |
| Texas | 34 | 1 | 455 | 45.1 | 54.9 | 7.0 | 93.0 | |
| Utah | 5 | 1* | 425 | 38.8 | 61.2 | 0.0 | 100.0 | |
| Vermont | 3 | 1* | 576 | 68.4 | 31.6 | 100.0 | 0.0 | |
| Virginia | 13 | 2 | 1669 | 50.6 | 49.4 | 64.5 | 35.5 | |
| Washington | 11 | 2 | 1306 | 57.4 | 42.6 | 100.0 | 0.0 | |
| West Virginia | 5 | 1* | 410 | 45.1 | 54.9 | 8.0 | 92.0 | |
| Wisconsin | 10 | 1 | 974 | 56.2 | 43.8 | 99.7 | 0.3 | |
| Wyoming | 3 | 1* | 465 | 43.0 | 57.0 | 1.7 | 98.3 |
* An older poll was used (i.e. no recent polls exist).
Details of the methods are given in the FAQ.
The most recent analysis in this and other match-ups can be found from this page.
