The latest CNN/ORC poll released today shows a wider lead for President Obama than the previous CNN/ORC poll but it is doubly skewed. It massively under-samples independents while it also over-samples Democratic voters. The CNN/Opinion Research Corp. poll official reports Obama at 52 to percent and Mitt Romney at 46 percent. Unskewed, the data reveals a 53 percent to 45 percent lead for Romney.
This new CNN/ORC survey, unlike many other analyzed, not only over-samples Democratic voters, but also massively under-samples independent voters, to produce a result more favorable to Barack Obama. This survey's sample includes 397 registered Republicans and 441 registered Democrats. But the survey included a total of 822 registered voters, leaving only 37 independent voters at most. The survey clearly under-sampled independent and Republican voters.
Among the Democrats survey, 97 percent favored Obama while three percent support Romney. The Republicans surveys chose Romney by a 96 percent to two percent margin. Those margins display a high degree of party loyalty in each party for its candidate, which is plausible in a campaign like this one where both sides are focusing heavily on boosting turnout among their base. Independents, who are massively under-sampled in this survey, support Romney by a 54 percent to 40 percent margin.
The sample for the CNN/ORC poll includes 50.4 percent Democrats and 45.4 percent Republicans and appears to have only 4.2 percent independents. This means independents are under-sampled 25 percent while Democrats are over-sampled 12.1 percent. Both of those are larger variations in sampling than seen in most polls that are likewise skewed by such sampling variations.
Rasmussen Reports recent reporting of partisan trends among voters, based on tens of thousands of voters surveyed, showed the voting electorate made up of 35.4 percent Republicans, 34.0 percent Democrats and 30.5 percent “Unaffiliated” or independent voters. Clearly 6.5 percent of a sample as independents is a large under-sampling of those voters compared to 30.5 percent.
Unskewing this data to make up for the likely 25 percent under-sampling of independent voters shows the results are quite different. With the weightings of independents, Democrats and Republicans conducted by the Rasmussen numbers, this poll's data would indicate a Romney lead over Obama of 53 percent to 45 percent. That is almost exactly the reverse of the 52 percent to 46 percent lead it reports in favor of Obama. The sampling skew of this poll actually reverses the result that should be shown by the data.