A new Gallup poll of declared and prospective Republican presidential candidates shows a crowded field led by former Massachusetts governor Mitt Romney and former vice presidential candidate Sarah Palin, who has yet to formally launch a campaign.

Romney ekes out a narrow plurality with 17 percent support and Palin is right behind him with 15 percent. Perennial libertarian outsider Ron Paul comes in third with 10 percent, followed by a cluster of candidates in the single digits.

The poll's results reflect a certain level of voter ambivalence, with 22 percent of respondents saying they have no preference. It is difficult to predict much given the rapidly evolving field of candidates: Mike Huckabee and Donald Trump led the previous poll and have since dropped out of the race.

When pollsters adjusted the data for the possibility that Palin drops out of the race, allocating her supporters' votes to their second-choice candidates, Romney carves out a larger lead. But a previous poll showed Romney's potential weakness, suggesting he is less well positioned than any other leading Republican candidate at this stage in the campaign.