Romney Wins G.O.P. Primary in New Hampshire Supporters of Mitt Romney celebrated his victory at Southern New Hampshire University in Manchester, N.H., on Tuesday night. MANCHESTER, N.H. - Mitt Romney swept to victory in the New Hampshire primary on Tuesday, turning back a ferocious assault from his Republican rivals who are working to slow his march to the Republican presidential nomination. As the polls closed here, Mr. Romney, a former Massachusetts governor, was projected as the winner, becoming the first Republican candidate since 1976 to win the Iowa caucuses and New Hampshire primary. Representative Ron Paul of Texas and former Gov. Jon M. Huntsman Jr. of Utah were battling for second, according to surveys of voters leaving the polls. Former Senator Rick Santorum of Pennsylvania and Newt Gingrich, the former House speaker, were trailing their Republican rivals, but already looking ahead to the next battle at the South Carolina primary on Jan. 21. Mr. Romney, who owns a house in the state and spent four years as the governor of neighboring Massachusetts, was considered a favorite son here. The outcome was not only a measure of strength for Mr. Romney, but also a test for challengers seeking a strong performance to propel them into the South Carolina primary. The New Hampshire contest was critical for Mr. Huntsman, who staked his entire candidacy on the state's primary. Mr. Paul, whose supporters dominated others in waving signs and banners on street corners throughout the day, was competing with Mr. Huntsman for independent voters, allowed to vote in either primary, who joined Republicans in helping to select a nominee to challenge President Obama. Mr. Santorum was hoping that his strong finish in Iowa, where he lost to Mr. Romney by eight votes, would give him additional momentum in New Hampshire. And Mr. Gingrich played down his expectations here on Tuesday and was looking ahead to his arrival in South Carolina on Wednesday. The advantages for Mr. Romney here were abundant, but there was one obstacle that loomed larger than any of his Republican rivals: The inclination of New Hampshire to knock a front-runner down to size. He urged voters to make him the first candidate to win the Iowa caucuses and the New Hampshire primary. "If I am president of the United States," he said, "I will not forget New Hampshire." The preliminary results of surveys of voters leaving the polls found that nearly half of the primary voters on Tuesday identify themselves as independents - or something else - and half consider themselves Republican. Half of the voters said they were conservative on most political matters, according to surveys of voters, while one-third said they were moderate. Only one in five voters said they were very conservative, and about one in 10 primary voters characterized themselves as liberal. In interviews at polling places across the state on Tuesday, voters acknowledged a degree of uncertainty in their choices. Several Republican voters said they were unsure who could accomplish the ultimate goal of winning back the White House. At the Rye Elementary School outside Portsmouth, Rose Cotronea, 50, said she had been mulling her choice for months with one thought in mind: "Someone's got to get rid of Obama." She considered Mr. Romney ("He's all right, but he feels too white bread") and Mr. Gingrich ("He's very bright, but I think he'll be ripped to pieces"). When Monday dawned and she still had not come to a decision, Ms. Cotronea made a 45-minute drive to see Mr. Santorum speak in Somersville. The experience made up her mind. "Just meeting him, seeing him speak, was really important," said Ms. Cotronea, a psychotherapist. These guys are so hypocritical. I want someone who is a man of character and values. She was not alone, according to the preliminary exit polls, which found that nearly half of New Hampshire voters had made up their minds within the last few days. Two in 10 said they were undecided until Primary Day. Trip Gabriel and Nicholas Confessore contributed reporting.