"We're all going to be dividing the vote and I think it will shake itself out when we get to South Carolina," said Gingrich, making the rounds of morning news shows with voting under way.
Gingrich also said he believed "the biggest story" in New Hampshire is that the former Massachusetts governor will fall short of "any reasonable expectation" in a state where he has been heavily favored for many months.
"New Hampshire is his third strongest state after Utah and Massachusetts," Gingrich told CNN in an interview. "If he can't do very, very well here tonight, I think it raises questions about his candidacy everywhere else."
The former House speaker said people expected New Hampshire to be Romney's for the asking, but "I don't think it's going to be much of a fortress."
In an appearance Tuesday morning on Fox News Channel's "Fox & Friends," Gingrich said he wouldn't press Romney on the former governor's comment about instances in which he enjoys firing people.
Gingrich said he thought Romney's remark had been taken "out of context" by critics and said he thought it wasn't "well-worded." The former congressman acknowledged that Romney actually was talking about people having the right to ditch a health insurer if they didn't like the service they were getting. But he also renewed his call on Romney to tell the public more about his time at the helm of a venture capital firm, Bain Capital, which Gingrich has charged went into some troubled companies, took money out and left people without jobs.
He called Romney's remark "clumsy," and said it illustrated that he'd be superior in a debate with President Barack Obama.
In the CNN interview, Gingrich also defended a series of anti-Romney ads that will be run by a super PAC in South Carolina in his behalf, saying Romney's negative advertising in Iowa forced his hand and that he wasn't going to "disarm."
Gingrich had a blitz of television appearances and 11th-hour campaign stops as he tried to whip up enthusiasm for his White House bid, following a disappointing fourth-place finish in Iowa. He planned to visit polling places in Manchester, Bedford, Merrimack and Hollis.
Gingrich has used New Hampshire as a staging ground to launch more aggressive attacks on Romney, labeling the GOP front-runner timid and assailing his time at the helm of Bain Capital. The most successful elections, Gingrich argues, are those in which the contrast between the candidates is wide.
"I really do believe a Reagan conservative has a better chance of defeating Obama than a Massachussetts moderate," Gingrich said late Monday at a town hall at a high school in Hudson that drew some 500 people.