Although former Massachusetts governor Mitt Romney has won both the Iowa caucuses and the New Hampshire primary, the upcoming South Carolina and Florida primaries will be critical in determining whether he can maintain his position as the frontrunner for the Republican presidential nomination, Harvard professors say.

Romney, a Harvard Law School and Business School alumnus, won the New Hampshire primary on Tuesday with 39 percent of the vote. Ron Paul, the runner-up, collected only 23 percent.

Despite the wide margin, government professor Theda R. Skocpol said, “I don’t think [New Hampshire] was decisive.”

“He did what we knew he was going to do all along,” Skocpol said. “South Carolina and Florida are the most important [upcoming] primaries.”

The winner of the South Carolina Republican primary has gone on to become the party’s presidential nominee in every election since 1980. Coming off the coattails of a win in New Hampshire, Romney is in a strong position headed into the South Carolina and Florida contests on Jan. 21 and Jan. 31.

But Skocpol noted that given South Carolina’s strong conservative leaning, voters in the state may be drawn toward Newt Gingrich and Rick Santorum, two of Romney’s more conservative opponents in the contest.

In a fundraising letter sent out to supporters on Wednesday, Gingrich emphasized the importance of the South Carolina primary. The letter said, “We’re going to do it next week in South Carolina or he’s almost certain to be the Republican nominee, whether conservatives like us want it or not. It’s up to you, right now.”

For many, however, Romney’s place on the Republican ticket already seems inevitable. According to a Gallup poll, Romney is the first choice among registered Republican voters nationwide. Another Gallup poll found that six in ten registered Republican voters believe that Romney will be their party’s eventual candidate, compared to 11 percent and 8 percent who predict Gingrich and Santorum, respectively, will clinch the nomination.

“I think he’s been the presumptive Republican nominee for a long time simply because there’s been a clear pattern,” Skocpol said. “He has money, he has a plurality of support, and all of the opponents who might assemble the non-Romney vote are dividing the vote.”

Trey Grayson ’94, the director of Harvard’s Institute of Politics, agreed that Romney will likely become the Republican candidate.

“Obviously from a delegate standpoint, he has a long way to go. But look at his campaign’s financial resources, organizational resources, and endorsements,” Grayson said. “No one else has emerged as a serious challenger for the nomination. If he finishes first or second in South Carolina, it’ll be hard to beat him in Florida.”

Yet pundits have frequently observed a lack of enthusiasm among voters toward Romney’s candidacy.

Antone Martinho III ’13, who said he is a conservative Republican, agreed with that view. “Republicans just don’t seem to like Romney,” he said. But he did not see a probable alternative. “In all honesty, I think Romney’s going to win. If anyone takes him, I think it’ll be Ron Paul. It would be exciting, but unlikely.”

—Staff writer Jose A. DelReal can be reached at jdelreal@college.harvard.edu.