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October 26, 2012

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The notion that Romney still had “momentum” weeks after his early October gains in the polls has now been debunked by numerous commentators and academics

While Brendan makes a number of good points, I think his word “debunked” is an overstatement. “Disputed” is a better word. Yes, a number of studies showed no improvement for Romney in the second half of October or even some improvement for Obama. OTOH some polls showed large gains for Romney in this period. E.g., the ABC/Washington Post poll showed a 4 point improvement for Romney for 10/22-25 as compared with 10/10-13. Gallup also showed a 4 point improvement over a roughly similar period. What happens when we look at all the major polls?

Here's a list of major poll results over time. By eye, Romney has still been improving. Here are two ways to see the trend. The average of the ten polls with a sample starting date of 10/15 or later has Romney 0.9 percentage points ahead, while the average of the ten prior polls is a dead tie. So, by this measure Romney did gain in the last half of October. Or, look for an even more recent trend by splitting the most recent 10 polls in half. The latest five have Romney ahead by an average of 1.8%. The prior 5 show an exact tie.

IMHO this doesn't definitely prove that momentum continued into the second half of October. There are too many uncertainties. But, I think it does demonstrate that recent momentum hasn't been disproved. The recent gains may turn out to be real.

(Cross-posted at CJR)

Incidentally, note how we're all affected by motivated reasoning. Being a Romney supporter, I gravitate to the polls that show Romney ahead. Meanwhile, Brendan and other academics, presumably supporters of Obama, believe the studies that show Obama winning.

Silver's model is based on state polls, while the RealClearPolitics main figure is an average of national polls. That may be the biggest reason why Silver shows a high likelihood of an Obama victory, while the RCP average shows Romney ahead by 0.8%.

One would think that the national polls would be the sum of the state polls. However, Sean Trende shows that the national equivalent of the current state polls would show Obama ahead in the popular vote by around 1.2% - 2.5%. Trende says he doesn't know why this inconsistency exists or which method is better.

See http://www.realclearpolitics.com/articles/2012/10/31/whats_behind_the_state-national_poll_divergence_115979.html

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