WASHINGTON -- If Herman Cain chooses to exit the presidential race, Newt Gingrich will likely see a modest increase in his lead over Mitt Romney in national polling. Two recent national surveys show that when pushed to choose, Cain supporters prefer Gingrich over Romney, reinforcing the trend in recent polling that shows Gingrich rising as Cain's support shrinks.
With speculation growing in reaction to Tuesday's news that Cain is reassessing his candidacy, the most direct evidence of the potential impact of Cain departing the race comes from opinion polls that ask his supporters how they might vote should their choices narrow.
One example is the most recent national Quinnipiac University poll of 1,039 Republican primary voters conducted in mid-November. On an initial vote preference question, Cain finished third (with 14 percent) behind Newt Gingrich (26 percent) and Mitt Romney (22 percent), with the other Republicans winning support in the mid to low single digits.
But in a later question about a hypothetical match-up between Gingrich and Romney, Cain supporters break for Gingrich over Romney by a 49 to 35 percent margin, with 16 percent uncertain, according to results provided to HuffPost by the Quinnipiac University Polling Institute. Among all Republicans, Gingrich tops Romney on the two-way match-up by a slightly narrower margin, 49 to 39 percent.
A just-released Economist/YouGov online survey of 326 likely Republican primary voters conducted Nov. 26-29 produced similar results. The initial vote question shows Gingrich leading Romney by a slightly wider margin (25 to 17 percent) than the Quinnipiac University poll, with Cain running third (at 15 percent) and the other candidates receiving single digit support.
But the survey also asks Republicans for their second choices. When the vote preference is recalculated, reassigning Cain's supporters based on their second choices, Gingrich has an even wider lead over Romney (32 percent to 19 percent). In other words, according to the YouGov poll, Cain's departure would increase Gingrich's support by 7 percentage points, but increase Romney's by only 2.
YouGov surveys are conducted online using an "opt-in" panel of respondents recruited to complete surveys, a methodology that is the subject of an ongoing debate. In this case, however, the results are mostly consistent with the Quinnipiac University survey, which is based on in-person interviews. Both confirm that Gingrich would benefit the most should Cain exit the race.
These results are also largely consistent with the overall polling trends this month. As illustrated by the HuffPost Pollster chart (below), which is based on all available national polls, the roughly 9 percentage point drop in Cain's support during November has coincided with an even bigger jump in support for Gingrich. Romney's support has remained essentially unchanged.
CORRECTION: The original version of this article cited an incorrect overall result for the Quinnipiac University poll's Romney-vs.-Gingrich question.