Despite his lefty leanings, Nate Silver of the New York Times is well respected by both sides for his exhausting statistical analyses of elections.
He wrote a post yesterday near and dear to my heart – the reliability of looking at polling averages to determine where a race stands.
This gets a little wonky at times, so if poll analysis bores you, move on.
In his explanation about what he calls the “uncanny accuracy of polling averages”, Silver includes an important caveat:
…we’re only looking at races in which at least two different polling firms published a survey in the 30-to-60 day window. If you have just one company polling a race, you don’t really have much of an average, properly speaking. Our model addresses this by assuming much greater uncertainty in cases where the polling data is very sparse.
Fortunately in Ohio, that isn’t a problem. In September alone, the Ohio Governor’s race was covered by eight different polling institutions.
According to Silver, his “538 snapshot” of the Ohio Governor’s race with 32 days to go sits at a 6.4% Kasich lead. The snapshot is what Silver considers “the best estimate of the current standing of the candidates”.
With that 6.4% lead in mind, Silver continues…
Gubernatorial candidates with a lead of between 6 and 9 points in the polling average, meanwhile, have a 9-to-2 record. If we combine their numbers with those for the Senate candidates, we find that candidates with a lead comparable to Mr. Toomey’s (between 6 and 9 points, with 30 days to go in the race) have 16 wins against 2 defeats, which corresponds to a 89 percent winning percentage.
But the bottom line is that, over the course of the past half-dozen election cycles, constructing a simple polling average has provided a very reliable indication of which candidates will win the general election in Senate and gubernatorial races. Polling deficits in the high single digits, with 30 days to go in the campaign, have only rarely been overcome. Candidates who trail by double digits in the polling average have almost never defied the odds. Even relatively small leads of 3 to 4 points can be surprisingly meaningful.
So even after the recent swarm of polling showing the race tightening, what chance does Silver give Kasich of winning the race?
I like those odds.
UPDATE: More from Silver on Ohio…
Ohio: It’s Everybody Poll Ohio! week, with four organizations, including The New York Times, having released polls there in the last few days. All the new polls show the same thing: a widening margin for the Republican senatorial candidate, Rob Portman, but a narrowing one for their gubernatorial candidate, John Kasich. We now show Gov. Ted Strickland, a Democrat, with a 13 percent chance to save his seat, up from 8 percent last week.
I’m sure some people will ask why Mr. Strickland is still at 13 percent and not higher, when the two polls released Tuesday show him only 1 point behind Mr. Kasich among likely voters. There are several reasons. First, while the polls show Mr. Kasich’s lead narrowing, they still show him with the lead, and even a small lead can be surprisingly meaningful with barely more than a month left in the campaign. Second, the model is not in a rush to discard some slightly older polls, like those from SurveyUSA and Quinnipiac University, which had given Mr. Kasich a double-digit advantage; if these firms resurvey the race and find a different result, Mr. Strickland’s chances should improve in our model. Third, it is hard for any incumbent governor to be re-elected in a state where unemployment exceeds 10 percent, and other Midwestern Democrats are faring poorly in gubernatorial contests this year.