Obama wins and Presidential Electoral Simulation predicts it

The current count for President-elect Obama has turned to 364 electoral votes now that North Carolina has finally clicked into the Democratic column. I was waiting for that to happen before I could crow about how my prediction of 364, based on the InTrade prediction markets, was correct. Honestly, I just used their data and made some pretty pictures and simulations to assuage my curiosity over just what the chances of a Democratic victory were.

I see that the great fivethirtyeight.com missed by those 15 electoral votes. In all seriousness, they seemed to have called much of everything else correctly, especially the popular vote.

Now to the transition team. President-Elect Obama picking Rahm Emanuel to be his Chief of Staff caused one of the submitters at Fark to quip:

"Obama officially offers the Chief of Staff spot to Rahm Emanuel. So they've got Matt Santos and Josh Lyman, now they just need CJ and Toby"

For West Wing fans who know that Josh Lyman's character was based on Rahm Emanuel and noticed the parallels of this election to the final election in the West Wing series, this is quite humorous.

Final Presidental Electoral Vote Simulation Predicts Obama win

It is no surprise that the final presidential electoral vote simulation based on the Intrade Prediction market data predicts a win for the Democrats and the Obama/Biden campaign. It has been trending that way for several weeks. Only 4 simulations out of 1000 show a McCain/Palin victory.

The median electoral vote from the simulations is 351, but the most frequent number is 364 electoral votes for Obama/Biden, which is my official prediction for the race. The table below shows that all of the states, according to the prediction market, have moved to strong Republican or Democratic except for Missouri, which is weakly Democratic at this point.


A plot of the electoral votes from the Intrade data over the past weeks shows that the Democrats have never been below 270 with a straight addition of the states. Though some weakly Democratic states would have left them with a deficit.

The plot of the median electoral votes and the fraction of simulations which resulted in a Democratic victory over the past few weeks shows that the lowest point in recent history was the week of September 16th.

Barring unforeseen circumstances, I think that the Democrats should emerge victorious. You can make that happen by remembering to vote.

Other sites show similar results using polling data:

FiveThirtyEight.com which has Obama at 348.6 electoral votes to McCain's 189.4 and the Democrats winning in 98.9% of his 10,000 simulations.

Electoral-vote.com has 286 electoral votes for Obama, and 225 for McCain with 27 in a tie. This site also uses state by state polling data.

RealClearPolitics.com has Obama with 278 electoral votes and McCain with 132 with 128 in the toss-up category. They use polling data. That is by far the most pessimistic result for the Democrats of these major polling and simulation websites. With no toss ups they have Obama with 338 and McCain with 200.

270towin.com is running very slow today. They use the last 1000 simulations in their visualizer to build up results that have Obama with 342 electoral votes and McCain with 196. They have the Democrats winning in 98.7% of their simulations. They also use probabilities of each state winning based on polling data with some clipping of the data. Even their 90% confidence interval has an Obama/Biden win with their most pessimistic number at 284.

The Truthisall 2008 electoral model has a final prediction with Obama winning by 76-64m votes; 367-171 EV; 53-45% vote share margin. They seem to be real concerned about election fraud and have a hard to understand election model with assignments for undecided voters.

What's your prediction?

One week to the election - Democratic electoral win in simulations

There is essentially not change from last week in the electoral vote simulations as predicted by the InTrade prediction market data for each state.

The median vote tally for Obama has crept up to 345, but the states in the strong and weak Democrat, and strong and weak republican columns have remain almost the same. With Indiana and Missouri wobbling back and forth but not changing party identities. MSNBC and others still try to make this look like a race, but the prediction markets say otherwise.

I will run the simulation again one more time next week before the election is over and then we can do some analysis.

Democrats maintain their formidable lead in Presidential Electroal. Vote Simulations

Barack Obama still holds a formidable lead in the presidential electoral vote simulations based on the state by state InTrade prediction market data. From today's results, the Democrats win 99% of the simulations and the median electoral vote count is 340.

There has been little change in the assignment of states to strong and weak categories except that previously weakly Republican Indiana has strengthened for McCain. If instead of the median we look at assigning the states based on the state by state prediction market data, the totals are 364 for Obama to 174 for McCain.

I imagine that the race will still tighten in these last two weeks. It will be interesting to see if that is reflected in the prediction markets.

Simulations asymptotically approach certainty for Democratic Electoral Vote Win

This week the electoral vote simulation pushes even closer to a certain Democratic electoral vote victory. Of 1000 simulations only 21 have the Democrats with less than 270 electoral votes based on the probabilities from the Intrade prediction markets. The chart below shows the distribution of 1000 simulations. 98% of the simulations yield a Democractic victory, and the median electoral vote count for Obama is 337.



I would guess that the Intrade prediction markets have digested all of the Obama vs. McCain polling data, the financial crisis and any other information about polling in the various states to slide even further over to the Democratic side in each state. This has the interesting effect of putting states that a few weeks ago were strongly Republican over into the strongly Democratic side. According to the Intrade prediction data the Democrats are weakly holding Missouri and North Carolina, never mind previously weak states like Nevada, New Hampshire, Ohio and Virgina that are strongly Democratic now, and the Republicans are weakly holding Indiana, as former battleground states become too solid to shake.


This data will be slightly different than the polling data since it is a prediction market site, but I still laugh when CNN or MSNBC tries to pretend we are still in a horse race when it looks like a solid Democratic victory is predicted at this point. I doubt the debate tomorrow will move anything one way or another. Three weeks to election day.

Presidential electoral vote simulation predicts Republican Victory

The Palin Republican Convention bounce seems to be having a continuing effect on the presidential electoral vote simulation based on the Intrade Prediction market data of September 16th. As described earlier, I use the Intrade data to generate a probability for each state of tghe Democrats winning that states electoral votes. I generate 1000 Monte Carlo simulations based on these probabilities.

This week the chart shows that the the Democrats win with more than 270 electoral votes only 46% of the time. This is the first time that the simulations predict the Republicans winning more than half of the time. I think that we could see this coming as the prediction markets and polls continue to digest Sarah Palin's popularity and McCain's bounce. FiveThirtyEight.com shows similar results based on their excellent simulations based on state polls, with only 44.6% of simulations with an Obama victory.

As a prisoner of Excel as my math, simulation and graphing program, I am jealous of Yahoo's new election tracker dashboard that uses either state polls or the Intrade prediction market data to show the electoral vote results. It made me notice something interesting about the Intrade prediction market data. If I just use that data, as Yahoo does, to predict whether a state will go Democratic or Republican, the results is that the Democrats win with 273 electoral votes. But the prediction markets have been shown to represent the collected estimated probability that the players expect for a particular outcome. So while Delaware options are at 95cents (on the chance of $1.00 if the option pays) for the Democrats which makes that a pretty sure bet, Colorado is 55cents Obama vs 47.6cents for McCain which makes that close to even odds. That's why I like my simulation approach better.

The table below (click it for larger and more readable) compiles the simple sum of the prediction market data and then breaks out strong states, those with 60% chance of one of the sides, vs weak states, those with less than a 60% chance for one of the sides. It is there where you can see the closeness of the race.


Remember that in the simulation even Delaware could go for the Republicans 5% of the time. Highly unlikely but possible, especially with the potential error of the data we are using. A state like Colorado could go either way. The progression over two weeks since Sept 2nd doesn't seem to put more electoral votes in play in the weak states (51 to 56), but it does seem to move some weakly Democratic ones to the weakly Republican column. This week the states that are weakly Democratic are Colorado, New Hampshire and New Mexico, while the weakly republican states are Nevada, Ohio and Virgina. On Sept 2nd the states that are weakly Democratic were Colorado, New Hampshire and Ohio, while the weakly Republican states are Nevada, and Virgina. As the pundits have said, Ohio and Virgina are going to be important, and even some Western states are going to have a role to play

Simulating the presidential election - state by state is best

There are a number of sites out there that attempt to predict the presidential election. I prefer the sites that add some simulation to the process so that we can see not just a prediction but the relative accuracy and sensitivity of the results to the input data.

The Presidential Vote Equation derived by Ray C. Fair uses the econometric approach which predicts just the Democratic and Republican popular vote share. Fair's simple regression showed that the important variables are incumbency for the person and party, typically a negative effect, and economic good times are good bad times are bad. This year if the economy stays bad the Democrats are favored, but it could be a dead heat if the economic bad news is not as bad as expected.

I think the best or most interesting predictors are the ones that examine the polls from many states to calculate state by state electoral votes because that is the way the president is chosen, not by popular vote. The best I have seen thus far is FiveThirtyEight.com (named for the 538 electoral votes). They work through the polls in every state and group like regions together to estimate polls for states when there is a long time between polls (Delaware, for instance, is in the "Acela" Mid-Atlantic group). They predict 307 electoral votes for the Democrats today (up from 303), comfortably more than the 270 needed to win. They also perform simulations based on the error in the polls to generate various scenarios. They have a democratic win in ~70% of the scenarios.

I took a crack at this approach using the Intrade prediction market data. Users of the site can purchase stock in a particular outcome, for instance, Delaware's electoral votes go to the Democrats. Users buy and sell their shares at values based on their confidence in the outcome. It has been shown that this is a predictor of the group's estimation of the probability of this occurrence. I took the probability of the democrats getting the electoral votes and divided by the sum of the either party getting the votes to generate a Democratic probability. Then I used the rand() function in Excel, if it beat the probability, votes went to the Democrats otherwise to the Republicans. Adding up all of the states yields the total electoral votes for the Democrats who need 270 to win.

(click picture or here for larger)

Thus my simulations show that, using the Intrade Sept 2nd data and assuming winner take all in each state (even Maine and Nebraska), the Democrats garner 270 electoral votes or more in 75% of the simulations. The most likely being 277, the median is 289. After the Republican convention is over we can see how this changes. Great care should be taken with these estimates since some of the states have only a few trades and thus the error in the estimated probability is high. I could try to factor that in to the simulation, but I feel the point is proven in principle and we can leave the heavy lifting to the folks that do it for a living, instead of for fun.