U.S. Senator Marco Rubio, emerging from the first Republican nominating contest of the 2016 presidential election as the party's leading mainstream candidate, faces a strong field of rival establishment figures in next week's New Hampshire primary.
Rubio, 44, from Florida, came in third at Monday's Iowa caucuses with 23 percent of the vote, making a stronger-than-expected finish and establishing himself as the alternative to front-runners Ted Cruz, 45, and Donald Trump, 69.
Conservative Cruz won the caucuses with 28 percent, four points ahead of businessman Trump, whose campaign has been marked by such controversies as his call to ban Muslims from entering the United States and a pledge to build a wall along the U.S.-Mexican border.
Evangelical Christians helped Cruz, a U.S. senator from Texas, to victory in Iowa, but he might struggle to win on Feb. 9 in New Hampshire where Republican voters have more secular and libertarian streaks.
Republican U.S. Senator Lindsey Graham said a recent hardening of Rubio's position on immigration and the strength of his anti-abortion stance might cost him.
“Running to the right to win Iowa is going to be a hard sell here in New Hampshire,” Graham, a supporter of Republican Jeb Bush, told Reuters in Rindge.
The son of Cuban immigrants, Rubio said on Tuesday he was the candidate to unite the Republicans at the Nov. 8 general election, when the party hopes to regain the White House after Democratic President Barack Obama's two four-year terms.
"People realized on the Republican side that we cannot afford - this country cannot afford - to lose this election, and that I give the party the best chance not just to unify our party but to grow it," Rubio told ABC's "Good Morning America" show from Manchester, New Hampshire.
Rubio, a fluent Spanish speaker, hopes to win back some of the Latino vote the party lost in recent years as it toughened its stance on immigration. A foreign policy hawk, Rubio advocates a tough approach to Iran, the Islamic State militant group and other U.S. foes.
Iowans who supported Rubio at the caucuses said they responded to his relatively positive message and viewed him as the candidate most likely to beat former Secretary of State Hillary Clinton, should she be the Democratic nominee.
Worries about such issues as immigration and terrorism have fueled the campaigns of Trump and Cruz.
"We've seen a campaign that's been characterized by candidates trying to exploit peoples' fears and anxieties and insecurities about the future. And those candidates ended up doing pretty well last night," White House spokesman Josh Earnest told reporters on Tuesday, speaking about the Republican field.
Concerns about the income gap and economic insecurity have also helped Democratic left-wing candidate Senator Bernie Sanders, 74, who narrowly lost to Clinton, 68, in Iowa.
Sanders' home state is Vermont, next door to New Hampshire, and that may give him an advantage in next Tuesday's primary. Clinton's razor-thin margin was the smallest in Iowa Democratic caucus history.
Clinton acknowledged she had to try harder to win younger Democrats, who backed Sanders in Iowa in large numbers. "I’m going to have some work to do to reach out to young voters, maybe first-time voters, who have to make a tough decision,” she told CNN.
Moderate Republicans besides Rubio, like former Florida Governor Jeb Bush, Ohio Governor John Kasich, and New Jersey Governor Chris Christie, are expected to do better in New Hampshire than they did in Iowa.
Christie on Tuesday accused Cruz and Rubio of lacking executive experience for the job of president.
“What do they do exactly in the United States Senate? They talk and they talk. They are not responsible for doing anything,” he said. “Marco gives a great speech and so does Ted, but that’s what they do. They make speeches,” Christie said at his campaign's New Hampshire headquarters in Bedford.
Bush, the brother of former President George W. Bush, took a similar line of attack at a town hall in Rindge, saying that Cruz and Rubio were "gifted in how they speak, but what about their life experiences?”
New Hampshire has a long tradition of bucking trends in presidential primaries.
Rubio might have to tweak his message for the state's audience, said Wayne Lesperance, director of the Center for Civic Engagement at New England College in New Hampshire.
"I think he will still emphasize a conservative message but a bit less focused on faith matters and more focused on fiscal issues, the border, and gun control. Those are hot-button items this cycle" with Republicans in New Hampshire, he said.
Opinion polls of Republicans show Trump leading nationally and in New Hampshire.
The outspoken real estate magnate, who dominated the Republican race for months, broke an unusual silence of more than 12 hours on Twitter after his defeat in Iowa. He said on Tuesday he did well in the Midwestern state despite having spent little on his campaign there.
"Because I was told I could not do well in Iowa, I spent very little there - a fraction of Cruz & Rubio. Came in a strong second. Great honor," he wrote on Twitter where he has regularly issued scathing criticism of his opponents.
(Additional reporting by Doina Chiacu, Susan Heavey and Mohammed Zargham in Washington, Ginger Gibson and John Whitesides in Iowa and Emily Stephenson in New Hampshire; Writing by Alistair Bell; Editing by Frances Kerry and Howard Goller)