A lot of people seem to be having a lot of angst about the fact that the polls are showing either a very slim Romney lead or an Obama lead. However, it seems that several of the major polls are making an unreasonable assumption that could easily affect the results.
Of the recent polls for which I have internal numbers, only Rasmussen’s turnout percentage assumptions are realistic. The other four polls use a sample that assumes an election turnout of between 86 and 93 percent. That simply is not going to be the case. From this small sample it appears that Rasmussen is not the outlier it is often accused of being. Instead, other polling organizations in the current RCP Average employ a likely voter screen that removes only 7% to 14% of registered voters from the sample pool, when we know that about 30% of registered voters are not going to show up to vote.
When a poll oversamples unlikely voters, it gives disproportionate weight to the unenthusiastic. In most years that pushes Republican poll numbers lower, at least until the only poll that counts: the one on election day. The presidential election of 2008 might have been an exception to that rule. But even if that were so, in 2012 it is Barack Obama who now has lukewarm support. Turnout simply is not going to match the expectations contained in most of today’s polls. And a lot of Democrats are going to be surprised by the results.
Even in 2008, when the Obama campaign was praised for bringing lots of new voters to the polls, overall turnout was only 64%.
Krumm is right, there is no way we are going to get 86-93% voter turnout this year. And any poll using such a leaky likely voter screen is not to be trusted.