In an interview with Politico the other day, Nate Silver (above), the popular polling analyst for The New York Times, tried to demystify the work he does:
“This is not wizardry or rocket science,” said Silver. “All you have to do is take an average, and count to 270. It’s a pretty simple set of facts.”
Silver concentrates on state polls, not national surveys. He averages the numbers in virtually all the polls in each state, makes a minor ajdustment or two, assigns each state to one candidate or the other, adds up the electoral votes and — voila! — projects an overall winner.
A few hours ago, Silver posted an ARGUMENT for why he thinks President Obama is likely — but not certain — to win the election:
Mr. Obama is leading in the polls of Ohio and other states that would suffice for him to win 270 electoral votes, and by a margin that has historically translated into victory a fairly high percentage of the time.
The argument that Mr. Obama isn’t the favorite is the one that requires more finesse. If you take the polls at face value, then the popular vote might be a tossup, but the Electoral College favors Mr. Obama.
So you have to make some case for why the polls shouldn’t be taken at face value.
Some argue that the polls are systematically biased against Republicans. This might qualify as a simple argument had it been true on a consistent basis historically, but it hasn’t been: instead, there have been some years when the polls overestimated how well the Democrat would do, and about as many where the same was true for the Republican. I’m sympathetic to the notion that the polls could be biased, statistically speaking, meaning that they will all miss in the same direction. The FiveThirtyEight forecast explicitly accounts for the possibility that the polls are biased toward Mr. Obama — but it also accounts for the chance that the polls could be systematically biased against him.
Silver goes on to deal with other challenges to the notion that Obama is likely to win. And, characteristically enough, he offers lots of charts and numbers to support his arguments.
I strongly recommend that you read the whole thing.