Lauren Feldman, an expert at American University on the political effects of late-night comedy, said if Palin were to appear on the late-night program, it is not clear whether would help the McCain-Sarah ticket.

"Appearances on late-night comedy shows are useful for candidates as a means to project their non-political personas, to make them seem more 'human' and in-touch with voters. Palin is not necessarily lacking in these areas," Feldman said in a statement. "She would benefit more from a strong, substantive performance in a more serious setting."

However, Tina Fey's impersonations of Palin -- which accentuate the candidate's folksy persona, her interview and debate performances, and her g-dropping, "gosh darnit" speaking style -- are likely to make Palin's negative traits and image characteristics more top-of-mind for viewers, which can indirectly contribute to a more unfavorable rating of the Republican ticket, Feldman said.

However, Feldman said Fey's impersonations will probably not hurt the Republicans because the "SNL" audience is not necessarily interested in politics.

The findings are scheduled to be published in the journal Political Communication.