2008 Presidential Election Simulation (II)

I last posted election simulation results a few weeks ago.  At that point Democrats were holding their heads in their hands as McCain coasted through a post-convention bump and the dominant news stories were about the "lipstick on a pig" comment and Obama's supposed kindergarten sex ed program.  Since that time we have had a financial crisis, McCain "suspended" his campaign, we have had presidential and vice presidential debates, and today a wall street/economy bail out plan finally passed in the House, after it was initially rejected.  In all of this time there has been a great deal of movement in poll numbers, generally in a favorable direction for Obama.

Here is another presidential election simulation based on current polling data, predicting what would happen if the election were held today.  Keep in mind that as polling numbers change in the next month, so too will these probability values.

When I previously explained my methodology, I may have glossed over the details a little bit.  Here is hopefully a clearer explanation of my procedure.

By taking the current polling margins I compute a win probability for each state based on a normal cumulative distribution function approximating that of Charles Franklin's.  His curve can be found here.  Below is my approximation of his curve, using the parameters mu=-1, sigma=6.8.  

I then use the current state-level polling data to determine win probabilities for each state.  I create two separate models, one based on the Real Clear Politics averages and the other based on the latest regression analysis margins from Pollster.com.

I then simulate 10,000 elections based on these probabilities.  The percentage of the time Obama gets more than 269 electoral votes is taken to be his overall win probability if the election were held today.

Here are the results:

Based on the margins of polling averages from Real Clear Politics, Obama wins an astonishing 98% of the time (average 328 electoral votes).  Note that results to the left of the dotted line are McCain wins while those to the right of the dotted line are Obama wins.

Based on the margins of pollster.com regression lines, Obama wins 93% of the time (average 312 electoral votes).

So at this point the race is Obama's to lose.  Nevertheless, after seeing such dramatic movement in the polls in the last three weeks we might expect that these numbers could shift back.  In fact, I expect Obama's lead to decrease in the next month if for no other reason than the fact that races tend to get tighter as elections get nearer.