One of the most startling developments in the fight for the Senate this year is that Michelle Nunn, the Democratic candidate in Georgia, has closed the gap with the Republican David Perdue. Her gains came after it was revealed that Mr. Perdue, a business executive, said in a deposition in 2005 that he was proud of his record of outsourcing.
But what if Ms. Nunn hasn’t really won any new voters at all? Oddly, a closer look at recent polls — the same ones showing Ms. Nunn making gains — raises that possibility.
A few weeks ago, I wrote that Georgia polls — all conducted before the outsourcing comments were reported — might be underestimating Ms. Nunn because they were understating the black share of the likely electorate.
Three weeks later, the polls show Ms. Nunn and Mr. Perdue locked in a dead heat, and all of Ms. Nunn’s gains are attributable to changes in the racial composition of likely voters.
The six polls since reports of Mr. Perdue’s outsourcing remarks show black voters representing 29 percent of the electorate, and white voters representing 63.4 percent of the electorate. That’s more diverse than the previous polls, and neatly in line with Upshot estimates. The polls before the outsourcing remarks were published showed black voters at 26.2 percent of the electorate, and white voters at 65.4.
Recent Polls Account for a More Diverse Georgia Electorate
The racial composition of likely voters in recent Georgia polls is more in line with expectations.
There is no evidence that vote preferences have shifted by any discernible amount. The five recent polls with a cross-tabulation of the vote by race show Ms. Nunn trailing by 37.1 points among white voters, while the five old polls showed Ms. Nunn trailing by 36.9 points among those voters; the five recent polls show Ms. Nunn ahead by 76 points among black voters; the five old polls showed Ms. Nunn ahead by 75.7 points among black voters.
The most recent wave of data from the New York Times/CBS News/YouGov online panel offers additional evidence. Nearly 92 percent of past respondents gave the same answer in Georgia as they did last time, making Georgia’s electorate the third-most stable of the Senate battlegrounds. Most of the changes among the voters who did switch their answers canceled out: In the aggregate, Ms. Nunn gained about a half-point among past respondents.
Why did Ms. Nunn gain in the polls? The best explanation is the screening of likely voters. It seems that more black or fewer white respondents are being deemed likely to vote. The outsourcing comments could be responsible: Mr. Perdue’s comments might have raised the enthusiasm of Democratic-leaning voters, causing more to pass through likely-voter screens, or diminished the enthusiasm of Republican-leaning voters, causing fewer of them to pass through likely-voter screens.
It is even possible that the shift wasn’t because of the outsourcing comments at all, but because more irregular, disproportionately Democratic-leaning voters were tuning into the race as the election neared. Nearly 400,000 Georgians have already voted.
There is precedent that the swing was really just the result of likely-voter screens. In the 2000 election, the political scientists Robert Erikson, Costas Panagopoulos and Christopher Wlezien found that many shifts in the race reported by Gallup during October 2000 were because of changes in the composition of likely voters, not shifts in the preferences of registered voters. A similar phenomenon might have deflated Barack Obama’s standing after the first presidential debate in 2012.
Georgia Election Preview »
Now that the polls show an electorate more representative of what we should expect in November — with the polls not missing a large number of black voters — there’s less reason to believe that Ms. Nunn’s support is being underrepresented. That’s clarifying and, in a way, reassuring for Mr. Perdue and his supporters: The bad news is out of the way for them, and there shouldn’t be any nasty surprises on that front on Election Day.