The chief difference between the surveys was the share of likely voters that identified themselves as Democrats, Republicans and independents, attitudes that both polls measured by asking an identical question.
In the Post poll, self-identified Democrats outnumbered Republicans 35 percent to 27 percent among likely voters, while Quinnipiac found Republicans with a two-point edge in party identification, 31 percent to 29 percent. Previous Quinnipiac polls this fall have found Democrats with a five- to eight-point edge on identification among likely voters; a September Post poll found Democrats with a seven-point edge.
Because neither poll was weighted to match a predetermined partisan composition of voters — a controversial practice among pollsters — the difference reflects a basic divergence in the two surveys’ samples of likely voters in the state. In Virginia, the partisan makeup of voters in recent elections has varied substantially across elections.
In the 2009 governor’s race, exit polling showed Republicans outnumbering Democrats by four points as Republican Robert F. McDonnell cruised to a double-digit victory. But Democrats held six- and seven-point advantages in party identification in 2008 and 2012, respectively, when the commonwealth voted for President Obama.
Two additional university-sponsored polls were released Wednesday, each with differing leads for McAuliffe and estimates of the partisan composition of the likely electorate.
A Roanoke College poll shows a 15-point advantage for McAuliffe over Cuccinelli among likely voters with a corresponding partisan makeup of 36 percent Democratic to 27 percent Republican, similar to the Post/Abt-SRBI poll. A poll from Hampton University reports a six-point lead for McAuliffe among likely voters, with a narrow split of 35 percent Democratic and 33 percent Republican likely voter composition, more closely reflecting the Quinnipiac poll.
Cuccinelli’s team seized on the Quinnipiac result Wednesday as evidence that the race isn’t over.
“For the past several weeks, political pundits have written off Ken Cuccinelli well before any polls have opened or closed, but we have consistently maintained that we know this is a margin race as exhibited in today’s Quinnipiac University poll,” said Cuccinelli strategist Chris LaCivita.
McAuliffe spokeswoman Rachel Thomas cited the Quinnipiac survey as evidence that “mainstream Virginians continue to side with Terry’s common-sense policies to grow the economy and his commitment to working in a bipartisan way to create jobs in the commonwealth over Ken Cuccinelli’s extreme tea party agenda.”
McAuliffe has been ahead in every publicly released independent poll since July, and nearly every survey in the past two months has shown the Democrat leading between five and nine points among likely voters. Support for Robert Sarvis, the Libertarian candidate, has hovered around 10 percent — he is at 9 percent in the Quinnipiac survey — although many polls have indicated that his backers are less certain of their vote than McAuliffe’s and Cuccinelli’s are.
The Quinnipiac poll was conducted Oct. 22-28 among 1,182 Virginia likely voters and has a margin of sampling error of plus or minus 2.9 percentage points. The Hampton University survey was conducted Oct. 24, 26 and 27 among 800 likely voters and has a 2.9-point margin of error. Roanoke College surveyed 838 likely voters Oct. 21-27 and has a 3.4-point margin of error. The Post poll was conducted Oct. 24-27 among a random sample of 762 likely voters, and has a 4.5-point error margin. All polls were conducted by calling samples of land-line phones and cellphones.
Peyton M. Craighill contributed to this report.