David Moore | November 3, 2008
On "All Things Considered" Sunday night, Andrew Kohut, director of the
According to Kohut, Obama was up by just 7 points among likely voters in the latest Pew poll, 49 percent to 42 percent, down from the 15-point lead he enjoyed the previous week. The NPR anchor asked Kohut to explain the dramatic decline in Obama's lead. "There are two things going on," he said. "First of all, John McCain has made some gains among whites and he's made some gains among independent voters. The other thing - McCain is enjoying the typical boost we get when we narrow the sample from registered voters to likely voters."
Actually, Pew has been reporting the results among likely voters since early September, and the decline in Obama's lead occurred among Pew's likely voters - which favored Obama by 53 percent to 38 percent in the Oct. 23-26 poll. The 4-point drop in Obama's support and 4-point gain in McCain's support found by the Oct. 29-Nov. 1 poll could not be attributed to narrowing the sample from registered to likely voters, given that both sets of results were based on likely voters. (See Pew's chart here.)
This misinterpretation of the data comes in the wake of Pew's previous two October polls, which were clearly outliers compared with other national polls conducted in the same time periods. Other polling organizations in mid and late October showed Obama with only half the lead that Pew did, so when Pew's last pre-election poll found only a 7-point lead, that finally brought Pew back into line with other polls.
It may be, as Kohut suggests, that McCain picked up support among whites and independent voters - though it is worth further research to explain why none of the other polls report the same dramatic change. In any case, whatever the mysterious causes of Pew's outlier results, followed by the sudden bounce back into line with other polls, this unusual fluctuation cannot be easily explained away as a change from registered to likely voters.