I was out of town over the weekend, so this week's simulations are a little later than last week's. As in the past, I'm taking data from Votemaster Andrew Tanenbaum's www.electoral-vote.com and running a simulation of 10,000 elections each, using both the 4% margin of error common to most state polls and a 12.4% margin of error, the latter coming from a linear regression of errors in 2004 polling data in predicting the final outcome.

This week's data:
4% Margin of Error
Obama wins 99.87%, averages 315.6 EV
McCain wins 0.08% averages 222.4 EV
Electoral tie 0.05%

12.4% Margin of Error
Obama wins 94.2%, averages 310.1 EV
McCain wins 5.4%, averages 227.9 EV
Electoral tie 0.4%

The standard caveats apply: we're still just under 4 months away, and many of the most recent polls are rather old.  The 4% margin of error case is at best a snapshot of the current state of the race: that allows only for variation caused by sampling error, not the possibility that opinion might shift during the course of the campaign due to outside factors.

I intended the larger margin of error to allow for that as well, but I strongly suspect it also overstates Obama's chances of winning, because my model is assuming each state's result is a completely independent trial. It is more likely that if general public opininion is shifting, it will tend to shift in the same direction in most states, making it more likely for McCain to come back (or for Obama to win in a larger landslide).

Individual states have bounced around a bit, but really not much has changed since Obama got a bounce from clinching the Democratic nomination: he's been winning nearly 100% of the current snapshot model, and about 95% of the larger margin of error for the past month. This week is no exception, as there are a few new polls which mostly cancel each other out in effect.

Missouri is a tight battleground state, and this week had contrasting polls, with Rasmussen finding McCain up by 5, while Research 2000 gives Obama the same 5 point edge. Following the Votemaster's algorithm, these two polls get averaged to make Missouri a toss-up, an improvement for Obama over last week, where recent polling had McCain slightly ahead. Earlier polls had given Obama a small lead, so this one truly looks like it could go either way. But it's one of an increasing number of "must win" states for McCain if he's going to have any serious chance of getting 270 electoral votes.

Another new data point is the first North Dakota poll since April: Rasmussen shows a 43-43 tie. McCain had a 6 point lead before in a Dakota Wesleyan poll, while the only other North Dakota poll was by Survey USA in February, showing Obama up by 4. This shifts ND from likely McCain to a tossup, another favorable development for Obama.

Rasmussen has McCain trailing by just 5 in its latest poll of New Jersey, which gives McCain a glimmer of hope he could take the Garden State, and their survey of Washington shows Obama's lead falling to 8, the first time he's led by less than 10 since late May. Rhode Island, Illinois, and Maine also have recent polls showing Obama's lead shrinking, but in each case his lead is well above 10%, so Obama wins these states virtually all the time in both simulations. The Rasmussen poll in Illinois is just the second of this matchup, and it gives Obama a safe 13 point lead, but one much smaller than the 29 point lead Survey USA saw in February. The only other new poll released this week is from Alabama, where Capital Survey has McCain up 49-36, his smallest lead of the season.

The overall map remains favorable to Obama: even though Florida is currently quite solidly in the McCain column, Obama wins overall quite comfortably. And there's evidence trickling in from Mountain West states like Montana and North Dakota that the 50-state strategy is chipping away at the GOP base. Without a significant public opinion shift in his favor, McCain will lose.