Sunday, September 21, 2008

McCain's Still Ahead

Well, sort of. I guess. Maybe. But I'm not sure. The national tracking polls have definitely been trending towards Barack Obama over the past five days but this national trend isn't necessarily in evidence at the state level. A good example of this is in Ohio where a plethora of polls suggest that there has been very little movement one way or other over the past 10 days. Another example is in Missouri where three polls taken by three different organizations over the last eight days show are within one percentage point of each other. This discontinuity between the national and state polls is also noted by Nate Silver on the website. Here is my take on the national popular vote shares between the two main candidates:

My model shows Obama ahead by 0.6 percentage points in the popular vote. This compares with an Obama lead of 2.2 percentage point spread in the model. Although both of our models showed McCain with a lead of about 2 percentage points just a few days ago, the model has been more sensitive to the polling movement at the national level than has my model and has been more quick to swing to the other direction. It's possible that the model puts more weight on the national polls than does my model, the latter which weights the national polls at about one third and the state polls at about two thirds. While Obama is ahead in the popular vote in my model, McCain still hold the same 10 electoral vote lead he has held for the past several days:

The reason for McCain's continued lead is an increasingly slender edge in Colorado, Missouri, Ohio and Virginia:

The four closest states have a total of 53 electoral votes, enough to give Obama 317 votes and a comfortable lead if all of these states flip. At this stage in the campaign, it looks like these four states may well hold the key to the election.

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