The debate has been amplified as the pace of public polling has accelerated after party conventions. Pollsters are finding diverging results, with consumers of political media left to decide which surveys better reflect the reality on the ground -- or to accept the polls most favorable to their partisan leanings. New, less expensive methods for taking polls have led to a proliferation of surveys with varying results, so both sides have ample data to fit their desired narrative.
Gripes about the party-ID composition of poll samples are certainly not new: Eight years ago, Democrats were claiming polls showing a surge in Republican identification did not accurately reflect the makeup of the electorate.
Now, it's Republicans making the case their voters are undersampled.
Schwartz, whose institute conducts polls in battleground states for CBS News and The New York Times, asserts that pollsters who weight according to party identification could miss the sorts of important shifts in the electorate that could be determinative.
"A good example for why pollsters shouldn't weight by party ID is if you look at the 2008 presidential election and compared it to the 2004 presidential election, there was a 7-point change in the party ID gap," Schwartz said. Democrats and Republicans represented equal portions of the 2004 electorate, according to exit polls. But, in 2008, the percentage of the electorate identifying as Democrats increased by 2 percentage points, to 39 percent, while Republicans dropped 5 points, to 32 percent.
Asked specifically about GOP complaints regarding the party-ID composition of public surveys, Schwartz said: "They're the ones trailing in our swing-state polls."
"There are more people who want to identify with the Democratic Party right now than the Republican Party," he added.
Many Republicans, however, think pollsters are wrong to assume their results, which in some cases mirror the 2008 electorate, are accurate.
"Far too many of the public and media polls have set their likely voter screens and models to something looking more optimistic than the 2008 turnout model," GOP consultant Rick Wilson wrote in Sunday's New York Daily News, "which even Obama's most dedicated partisans think is highly unlikely."
John McLaughlin, a Republican pollster and consultant to GOP candidates, told the conservative National Review last week that Democrats are lobbying media pollsters "to weight their surveys to emulate the 2008 Democrat-heavy models."
"The intended effect is to suppress Republican turnout through media polling bias," McLaughlin said.
Lee Miringoff, director of the Marist College Institute for Public Opinion in Poughkeepsie, New York, is unconvinced. "Why would pollsters want to look inaccurate?" Miringoff asked rhetorically in a phone interview.
Miringoff, who is conducting three battleground-state polls each week for NBC News and The Wall Street Journal, called the focus on party identification "too narrow."