"Gallup has him just teetering on the little teeter-totter at 50% and they're doing everything they can -- they're upping the sample to black Americans -- to keep him up at 50% in the Gallup poll," Limbaugh said on today's broadcast.

Limbaugh did not give any details about how he arrived at his conclusion about Gallup's methodology in the transcript of the show available on his website.

Gallup's Nov. 9-15 survey had Obama's approval rating at 53 percent while 39 percent disapproved of his performance and 8 percent expressed no opinion.

Limbaugh pointed to a Fox News/Opinion Dynamics poll conducted Nov. 17-18 putting the number of voters who approve or disapprove of Obama at 46 percent each, with 8 percent undecided. That compared to the 50 percent who approved of his performance in late October, while 41 percent disapproved.

Two other polls this week - by Quinnipiac University and Public Policy Polling - had Obama just under 50 percent. Quinnipiac's put his job approval number at 48 percent and PPP had it at 49 percent.

Quinnipiac's Peter Brown said of his poll that "Although President Obama's job approval rating is below 50 percent for the first time nationally, it is not statistically different from his 50 percent approval rating in October. Nevertheless, in politics symbols matter and this is not a good symbol for the White House."

Frank Newport, the editor in chief of Gallup, issued a statement saying, "Rush Limbaugh stated on his radio program Thursday that several polls have shown President Obama's job approval rating to be below 50%, while Gallup's has not (by "upping the sample of black Americans")...This statement is a complete and inexplicable fabrication. Gallup has a 70-year history of providing unbiased, scientific measures of public attitudes. Gallup is not now, nor has it ever, modified its data in order to achieve any desired result."