Former Massachusetts Gov. Mitt Romney leads a pack of four Republicans who are likely to win New Hampshire's primary, one of the state's top GOP figures said Wednesday.

Former Gov. John Sununu, who also recently wrapped up a term as chairman of the Granite State's Republican Party, said that Romney, former Minnesota Gov. Tim Pawlenty, Mississippi Gov. Haley Barbour or Indiana Gov. Mitch Daniels were the four most likely to win the first-in-the-nation primary in 2012.

"I suspect it'll be one of the four governors or former governors," Sununu said on ABC's "Top Line" webcast, naming Romney, Pawlenty, Barbour and Daniels.

Of them, "I think Mitt Romney is at the head of the pack of four," Sununu added.

The former governor is a significant figure in the state's Republican politics, and has been willing to speak candidly about his assessment of the Republican field heading into 2012.

Sununu has said, for instance, that he would actively work against Jon Huntsman, the former Utah governor, due to his service as President Obama's ambassador to China. The former state GOP chairman also lashed out at former House Speaker Newt Gingrich (R-Ga.).

"I just keep having run through my mind that television ad of him sitting with Nancy Pelosi telling us that we need some kind of carbon tax or other kind of crazy legislation," he said of Gingrich, referring to the environmental TV spot he did with the Democratic former Speaker.

He also questioned whether some of the additional candidates considering a run, including former Alaska Gov. Sarah Palin, were especially serious about campaigning.

"If you have a serious chance of running for president and winning, it's the hardest things you do in the world. If you don't have a chance of winning, it's one of the most fun things you can do in the world," he said.

Sununu ducked a question about into which camp Palin would fall, only saying it's up to candidates to decide.