Last week, the Gallup Organization provided more fodder for the debate over whether this year’s polls are skewed due to a systematic over-representation of Democrats in the samples. If Gallup has it right, Governor Romney’s lead may be several percentage points greater than the most recent round of polls suggests.

Gallup reviewed all of its interviews with “likely voters” conducted since October 1. Its conclusion: “The composition of the electorate for the 2012 presidential election is looking quite similar to what it was in 2008 as well as 2004.” Indeed, whether the sample is broken out on the basis of race, gender, level of education, or geographic location, the percentage of likely voters in each subset is no different than it was four years earlier.

But Gallup uncovered one very significant shift in this year’s voting electorate. There has been a remarkable movement toward the Republican party. As Gallup reports:

The largest changes in the composition of the electorate compared with the last presidential election concern the partisan affiliation of voters. Currently, 46% of likely voters identify as Democrats or lean Democratic, compared with 54% in 2008. But in 2008, Democrats enjoyed a wide 12-point advantage in party affiliation among national adults, the largest Gallup had seen in at least two decades. More recently, Americans have been about as likely to identify as or lean Republican as to identify as or lean Democratic. Consequently, the electorate has also become less Democratic and more Republican in its political orientation than in 2008. In fact, the party composition of the electorate this year looks more similar to the electorate in 2004 than 2008.

If anything, Gallup understates the case. In 2008, Democrats enjoyed a decisive ten-point advantage in partisan affiliation, 39 percent to 29 percent. When undecided voters were pushed to choose a party, the Democrats’ edge grew by another two points, to 54 percent to 42 percent. Yet in the Gallup polls conducted since October 1, the two parties have pulled even, with Republicans actually ahead by a statistically insignificant percentage point, 36 percent to 35 percent. After being pushed to choose a party, likely voters give the Republicans a further boost, resulting in an overall three-point advantage of 49 percent to 46 percent.

If you are keeping score, in slightly less than four years President Obama has presided over an eleven-point decrease in his party’s standing with the American people, 15 points if you include those voters who “lean” one way or the other.

The Pew Research Center has posted party identification data going all the way back to 1929. The data series suggests that this deterioration in the Democrats’ standing with American voters is nearly unprecedented. The only comparable meltdown occurred during the tumultuous years of the Vietnam War and the birth of the Great Society under LBJ, when the Democrats also suffered an eleven-point loss relative to their Republican rivals.

If you are wondering which president defied the odds and steered his party forward during his time in office, try Ronald Reagan. From 1981 to 1988 the Gipper’s principled conservative leadership whittled the Democrats’ initial 14-point edge down to a mere five points.

To be sure, the most recent spate of national polls include more Republicans than did the surveys conducted earlier in October. Nevertheless, they still give more advantage to the Democrats than Gallup’s aggregate data suggest should be the case. ABC/Wall Street Journal’s most recent poll, for example, includes 34 percent Democrats and 30 percent Republicans, the Investors Business Daily poll sets the Democrats’ advantage at seven points (38 percent to 31 percent), and an Associated Press survey comes in two percentage points more Democratic than Republican. 

Correcting these polls so that there was a Republican edge in the sample of voters consistent with Gallup’s finding would hand Romney a lead between five to ten points. Imagine the run on smelling salts at Mother Jones and MSNBC if that were to happen?

— Michael G. Franc is vice president of government studies at The Heritage Foundation.