Trying to explain why Gallup poll seems so out of whack

Today's tracking poll gives Romney a 7-point lead (52-45), which is nowhere near any of the other national polls that, as a group, has the race about even. The electoral vote projections generally give Obama a small edge. The NYT's Nate Silver says that Gallup has a history of wild swings - and of being wrong.

In 2008, the Gallup poll put Mr. Obama 11 points ahead of John McCain on the eve of that November's election. That was tied for Mr. Obama's largest projected margin of victory among any of the 15 or so national polls that were released just in advance of the election. The average of polls put Mr. Obama up by about seven points. The average did a good job; Mr. Obama won the popular vote by seven points. The Gallup poll had a four-point miss, however. In 2010, Gallup put Republicans ahead by 15 points on the national Congressional ballot, higher than other polling firms, which put Republicans an average of eight or nine points ahead instead. In fact, Republicans won the popular vote for the United States House by about seven percentage points -- fairly close to the average of polls, but representing another big miss for Gallup.

Silver, who provides way more technical analysis than you'll probably need, suspects that Gallup's polling model may explain the wild swings and often inaccurate readings. But he does not discount the survey entirely.

You should consider it -- but consider it in context. The context is that its most recent results differ substantially from the dozens of other state and national polls about the campaign. It's much more likely that Gallup is wrong and everyone else is right than the other way around.

Earlier:Have the Gallup pollsters lost their minds?