Nicole Gaudiano

USA TODAY

MANCHESTER, N.H. — Just like Iowans, New Hampshire voters have been inundated with campaign ads and visits from presidential candidates. And as the Iowa caucus results rolled in Monday night, they braced for the national spotlight to shift to the Granite State, which holds the first-in-the-nation primary on Feb. 9.

"Our phone rings off the hook all day," said Tyler Isabelle, 21, an employee at the Red Arrow Diner, a frequent stop for candidates. "Robots and real people. All day and night. Everyone wants to know who everyone's voting for."

Both contests are critically important for the momentum they lend — or deny — to candidates hoping to remain competitive later. Since 1976, when Iowa's caucuses became the nation's first nomination contest, Bill Clinton has been the only candidate to make it to the White House without winning either Iowa or New Hampshire.

With Donald Trump leading comfortably in New Hampshire, the other GOP candidates are largely battling for second place.

RealClearPolitics' average of the latest polls puts Trump at 33.2%, or 21.7 points ahead of Texas Sen. Ted Cruz and Ohio Gov. John Kasich, tied at 11.5%. Former Florida Gov. Jeb Bush is averaging 10.3% and Florida Sen. Marco Rubio is averaging 9.5%.

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Democratic front-runner Hillary Clinton won the New Hampshire primary in 2008, but polls this time show her trailing Sen. Bernie Sanders, I-Vt., by an average 18 points. Clinton's support is stronger in the South, but experts say her candidacy could be damaged if she performs badly in the first two states.

"She just is not very trustworthy," said Katie Trott, 24, of Manchester, while eating lunch at the Red Arrow Diner. Trott, an assistant manager at a bakery, considers herself an independent and said she supports Sanders for the "hope" he brings and his free college tuition plan.

"I feel like he actually does want to fight for me," she said.

Iowa and New Hampshire take their roles in the nominating process seriously. New Hampshire has more registered Republicans than Democrats, but the state’s largest bloc consists of “undeclared” voters who can cast ballots in either party’s primary.

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The Iowa caucuses bring out state residents who are passionate about their political choices, and most everyone else tends to stay home. In New Hampshire, turnout is higher and includes primary voters who generally aren't as intensely political, said Andy Smith, director of the University of New Hampshire Survey Center and a political science professor.

Both states are largely white, and their Democratic electorates are upper-income and progressive. But there are stark differences on the Republican side, Smith said. Republican caucuses in Iowa are dominated by evangelicals and social conservatives, while New Hampshire Republicans tend to be more moderate on political and social issues.

“That’s the primary reason why no Republican has ever won the Iowa caucuses and the New Hampshire primaries in the same year, unless they were the sitting president,” Smith said. “They’re different political planets between Iowa and New Hampshire on the Republican side.”

Clayton Caron, 22, of Bow, N.H., a finance major at Bryant University in Rhode Island, is among those moderate Republicans. Caron likes Florida Sen. Marco Rubio, whom he described as "probably the most centrist" of the GOP candidates. But he also could go for Kasich.

"He's been able to balance his budget in Ohio," said Caron, a finance major at Bryant University in Rhode Island. "That's a big thing. We can't keep financing debt."

Kasich left Iowa early and spent the weekend campaigning in New Hampshire. New Jersey Gov. Chris Christie and Bush were also holding events in New Hampshire on Monday.

“If we do well here, we’ll be fine,” Kasich told reporters in Rochester, N.H. on Monday. “If it doesn’t work, folks, it was nice seeing you. It’s been fun.”

The GOP establishment candidate who does best in New Hampshire -- a competition among Kasich, Rubio, Bush and Christie -- presumably will attract money and support from mainstream Republicans worried about Trump and Cruz.

“There’s going to be an incredibly powerful ‘stop Trump’ movement,” said Fergus Cullen, former chairman of the New Hampshire Republican Party, who has endorsed Kasich.

While most people living in Iowa were born there, New Hampshire has a high population churn. A recent University of New Hampshire study of demographic, polling and voter registration data found more than 30% of potential voters in the Granite State either lived in another state in 2008 or were not old enough to vote.

Smith, a co-author of the study, said young voters — 129,000 New Hampshire residents celebrated their 18th birthdays between 2008 and 2015 — could change the political calculus, particularly on the Democratic side. And he said New Hampshire polls that rely on lists of registered voters or previous primary voters likely underestimate Sanders' potential advantage,.

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A CNN/WMUR-TV poll the university conducted Jan. 27-30, which did not use previous primary voters as a sample, gave Sanders a 23-point lead, fueled largely by voters under 35 and first-time primary voters. The problem for Sanders? Those groups are typically the least likely to vote.

“That really is the key impact that these new voters might make,” Smith said. “I think it’s going to be on the Democratic side and I think it’s likely going to benefit Bernie Sanders very strongly — if they show up.”

It could help Sanders that New Hampshire colleges will be in session on primary day, making it easier for students to get to the polls. College campuses will be a primary focus for Sanders' voter outreach efforts, but his campaign isn't taking support from anyone else for granted, according to Karthik Ganapathy, Sanders’ New Hampshire communications director.

“All it comes down to is getting out the vote,” he said. “It’s all been building up to this.”

Contributing: Chrissie Thompson, the Cincinnati Enquirer