Ohio Tightens in New Poll

The race for the all-important Buckeye State is getting closer with just 3 percent undecided, according to a new poll:

Mr. Obama has a 5-point advantage over his opponent among likely voters, with 50 percent to 45 percent for Mr. Romney. Last month, in the Quinnipiac University/New York Times/CBS News poll of Ohio, Mr. Obama led by 10 points.

In the current survey, only 3 percent remain undecided and 95 percent of those with a preference said their mind was made up. Of those who had already voted, 54 percent said they cast their ballot for Mr. Obama and 39 percent said they voted for Mr. Romney.

The poll was conducted Wednesday through Saturday night, after the second presidential debate held on Tuesday at Hofstra University in Hempstead, N.Y. Almost half (48 percent) said Mr. Obama won last week’s debate, 27 percent said Mr. Romney was better and 12 percent considered it a draw.

Nate Silver took a look at Ohio on Saturday:

The best number of the day for Mr. Romney was almost certainly the Public Policy Polling survey of Ohio, which had him down by one point there — improved from a five-point deficit in a poll they conducted there last week.

If this had been the only poll of the day in Ohio, Mr. Romney would probably have made an Electoral College gain on that basis, since the forecast is very sensitive to anything in Ohio. There was another Ohio poll, however, from Gravis Marketing, which showed a tied race. Isn’t that an even better result for Mr. Romney?

Not in this case, because Gravis Marketing polls have had a Republican lean of two or three percentage points this cycle. (Their prior poll of Ohio had shown Mr. Romney up by about one point.)

The FiveThirtyEight model adjusts for these “house effects” and so treats the Gravis Marketing poll as equivalent to showing a two- or three-point lead for Mr. Obama.

It also adjusts the Public Policy Polling survey of Ohio slightly downward for Mr. Obama — but Public Policy Polling has lost most of the strong Democratic lean that it had earlier in the cycle, and it has even been on Mr. Romney’s side of the consensus in a few states like Iowa and New Hampshire. We now calculate their house effect as being only about half a percentage point in favor of Mr. Obama.