DERRY, N.H. — Marco Rubio spoke to an overflow crowd of more than 700 Friday evening as his confident presidential campaign eyes a strong finish in the first-in-the-nation primary on Tuesday.

The Florida senator has risen rapidly in the polls here since finishing a surprisingly strong third in Monday's Iowa caucuses, and he's looking for a similar result in New Hampshire to cement his position as a front-runner for the Republican nomination. But the expectations are higher and the challenges greater. This time, third place probably isn't good enough; and Rubio on Saturday must navigate a prime-time debate in which everyone on stage will be gunning for him.

"This is not just your normal election. It is not just a choice between two political parties. This election is a referendum," Rubio told an audience that sat and stood through remarks that lasted for nearly an hour. "What you are going to be asked to decide on Tuesday night in New Hampshire, is what kind of country do you want America to be in the 21st Century?"

In discussions about Rubio's New Hampshire prospects, his campaign assesses the trajectory of the eight-day race in cautiously optimistic terms. But the senator's team has an air of confidence about it that was evident in the closing days of the Iowa contest, where Rubio surged to finish 1 percentage point out of second place and 6.2 points higher than where he stood in the final average. Rubio is currently running second in New Hampshire.

In Iowa, Rubio's primary opponent was Sen. Ted Cruz of Texas, as both contended for the votes of conservative Republicans.

In New Hampshire, Rubio's team believes its candidate has a broader universe to pull from. Cruz supporters are still fertile territory for Rubio, but so are voters leaning toward the three governors in the race — New Jersey Gov. Chris Christie, Ohio Gov. John Kasich and former Gov. Jeb Bush of Florida — and possibly Donald Trump, the celebrity businessman from New York leading all Granite State polls.

At least two undecided voters who were at Rubio's Derry event to window shop for candidates told the Washington Examiner that their final two choices had narrowed to Rubio and Trump. Eric Morrow, 43, of Derry, said he had been interested in the billionaire real estate mogul and reality television star. Why is he reconsidering and leaning Rubio? "Not much substance" with Trump, he said.

Others in the crowd made up their mind months ago, like Donna Babineau, 52, who said she might have voted for Christie if Rubio wasn't in the race. "Ideologically, I think we're the same," she said. "I'm third generation American, my family's from Canada, and [we have] similar backgrounds."

Rubio this week released a slew of New Hampshire endorsements, including that of Craig Benson, the last Republican to serve as governor of New Hampshire. Rubio's Granite State supporters say the movement to him by prominent activists and political figures in the state bodes well for the direction of his campaign with just days to go until the voting. But to close strong, Rubio is going to have to fend off hard-hitting attacks from rivals.

Spurred by backer Rick Santorum's struggle in a television interview this week to list what Rubio has accomplished in four years in the Senate, Bush, Christie and Kasich have unloaded on the Floridian, charging that he's too inexperienced to serve as commander in chief. Television ads have been cut, and the three chief executives, who are struggling in the polls here, are sure to raise the issue during Saturday's debate.

"He doesn't have the experience to make a tough decision," Bush told Fox News' Bret Baier during an interview on Friday. "Name one thing that he's done."

Republican sources say that this line of attack might normally pay dividends. New Hampshire Republicans over the years have shown a penchant for nominating candidates with long resumes. Sen. John McCain of Arizona won here in 2008; former Massachusetts Gov. Mitt Romney won the New Hampshire primary in 2012. But Rubio supporters say the attacks have amounted to little so far, and they did not appear worried that the charges would stick.

Given the governors' struggles to gain traction, trying to knock Rubio for being inexperienced looks desperate and amounts to a bunch of noise that voters are likely to discount. That was the case, at least, for Lane Brokaw, 65, a health care professional from Derry. He conceded that he would prefer a candidate with more experience than Rubio has. But he's sold on the senator, and the attacks on his supposedly thin resume haven't changed his mind.

"He's clearly the most electable. I believe the candidates sense that, and I believe that's why they will unleash fury [Saturday] night" at the debate. "They know that he's the most electable now. There was that galvanizing moment after Iowa," Brokaw said. "I do believe he might be the last great hope in the Republican Party to win the White House."