On Causation…

Nate Silver, 6/25:

If the media believes that Barack Obama is ahead by 5 points, then if a new poll comes out next week showing him ahead by 3, it will not get any attention. But if the media believes that Obama is ahead by 12 points, that same poll would create the perception of McCain momentum, and perhaps trigger a couple of days’ worth of bad press for Obama as whatever had been going on over the past couple of days of the campaign would be taken as the cause for his polling decline. It might lead to harsher treatment of Obama’s decision (flip-flop?) on campaign finance, for instance, or if Iran had been the subject of the week, as evidence that Obama wasn’t resonating with voters on foreign policy.

Matt Stoller, 7/11:

Some Evidence FISA Hurt Obama

Obama has dropped in the latest Newsweek poll. He’s gone from 51-36 over McCain to 44-41. The most striking piece of data though is that 53% of registered voters think that he has changed his position on key policy issues to try to gain political advantage since becoming the nominee.

That is stunning. Over half of the public, though perhaps has not heard of the FISA fight specifically, believes he shifts positions for political advantage. And why shouldn’t they? He did.

I’m sure Matt would like to believe that Obama’s FISA failure is the proximate cause of the Newsweek polling change. It’s unclear to me how he could actually believe that, though; FISA (as he notes) is a high salience issue for a small number of people, and a low salience issue for a much larger number of people, and moreover the initial Newsweek poll was a substantial outlier. Silver, as far as I’m concerned, is entirely correct; the next Newsweek poll was quite likely to show regression to the mean, and pundits (some of whom, like Matt, should know better) would inevitably blame that on either the most temporally proximate event or on a favored issue.

This is not to say that Obama won’t suffer some harm from the FISA decision. I’m not convinced, but it could happen. But to say that he’s already dropped nine points in the polls is absurd.