The new Bloomberg/Selzer poll, showing Trump up 5 in Ohio (44-39), is bound to get a lot of attention. Ann Selzer is considered a genius at polling her home state of Iowa and many will assume her polls in other states are just as impressive.
We cannot know for sure, but it seems there’s an implausible swing in GOP composition in this Ohio poll. Forty-three percent of respondents considered themselves Republicans (33 + 10 leaners), compared to only 36% self-identified Democrats (29 + 7).
In the 2012 exit poll, there were 7 percentage points more Democrats than Republicans, 38-31.
I know we’re not supposed to second-guess each individual poll that comes along. Still, a 14-point swing (from D+7 in 2012 to R+7 this year) just doesn’t seem plausible. In fact, the 2012 figure is probably more reliable than the 2016 poll, as an exit poll, by definition, consists of people who actually showed up to vote.