Obama’s EV and Popular Vote Win Probability is on the RiseAssuming that the election is held today (and is fraud-free), the Election Model projects that there is a better than
99% probability that Obama would win the election. His expected electoral vote margin is
330–
208 with a
51.46% two-party vote share. He also leads the
National model (based on the latest 5 national polls) with
52.57% of the vote — giving him a
99.7% popular vote win probability.
The EV win probability is a simple calculation: Obama won 4926 of 5000 simulated election trials. His
win probability is therefore
98.5% (4926/5000). View the Election Model
Electoral Vote Simulation Frequency chart. The model is a snapshot in time. Ideally, the weighted average vote shares would be identical in both the national and state models. But if they are, it’s just a coincidence; state polls lag the national polls. View the
State vs. National Vote Share Projection Trend.
The
base case scenario assumes that Obama will win
60% of the
undecided vote. And this is conservative; he is presumed to be the challenger, since McSame is running for the third Bush term). Note that the
national polls lead the state polls, so that we can expect a rise in Obama’s expected EV and win probability. The national model also assumes that he will win 60% of the undecided vote. The probability that he will win the popular vote is over
99% — again assuming zero fraud, fairly accurate polls with the election held today.
If Obama captures just
50% of the undecided vote, he is expected to win by 311–227 EV with a 50.6% vote share and a 96% win probability. The probability of winning the electoral vote is very close to the probability of winning the popular vote. In other words, if the projected vote share is nearly tied, the probability of winning the electoral vote will also be close to 50%.
Democrats are strongest in high EV urban states, and Republicans are strong in low EV rural states. That’s why Obama can win the Electoral vote with slightly less than 50% of the total popular vote. The
sensitivity analysis (see below) shows that if Obama wins 40% of the undecided vote, he will have 50.0% of the 2-party vote, 290 electoral votes and an 80% win probability.
The
fivethirtyeight.com site projects Obama with a 311.5–226.5 EV lead and a 74.4% win probability. Obama would surely win more than 74% of the trials in a Monte Carlo simulation with that expected EV split, unless they are factoring in a fraud component without saying so.
As of Sept. 22,
electoral-vote.com has Obama leading by
273–
265;
realclearpolitics has Obama by
219–
189 (130 tossup). But the
2008 Election Model (
EM) has Obama leading by
330–
208. Why the difference?