Across New Hampshire, as the Democratic presidential candidates make their closing arguments ahead of Tuesday's first-in-the-nation primary, the latest polls suggest Bernie Sanders and Pete Buttigieg are in the lead, after finishing at the top in Iowa last week.

Sanders and Buttigieg are a study in contrasts. One is a 78-year-old Democratic socialist and the oldest candidate in the race. The other, at 38, is the youngest.

On Saturday in Keene, actor Michael J. Fox introduced Buttigieg as a "left handed, Maltese-American, Episcopalian, gay, millennial war veteran...and the next President of the United States."

Buttigieg delivered his now familiar case that he is best suited to unite the country — and to put "the chaos, corruption and the tweets" in the past.

"I am the candidate best prepared to defeat Donald Trump," Buttigieg said to the nearly thousand-person crowd that packed the auditorium at Keene State College.

Buttigieg is smooth on the campaign stump. He offers a positive vision even as he hits his opponents without naming them, alluding to Joe Biden's long experience and Sanders' "political revolution," and dismissing both.

"At a divided time in our country, I also don't think we can take the risk of excluding anybody from this effort by saying that if you're not either for a revolution or the status quo, then you don't fit," he said.

Buttigieg is riding a wave of momentum after his strong showing in Iowa. Now comes New Hampshire, where many voters say they're still making up their minds.

"I think a lot of people are sort of looking for the moderate alternative to Bernie Sanders," said Chris Bowen, who is backing Buttigieg. Bowen's been knocking on doors for the former mayor of South Bend, Ind., and talking to voters.

"I think the results in Iowa convinced them that Pete might be the most legitimate alternative to Bernie Sanders," he said.

Sanders also has the wind at his back, after apparently capturing the popular vote in Iowa, where election officials have yet to call the race.

"We won Iowa, and with your help, we're going to win here on Tuesday," Sanders said to a crush of supporters, who packed into a union hall in Concord.

Bernie Sanders speaks at the Our Rights, Our Courts Presidential Forum at the New Hampshire Technical Institute in Manchester, N.H. (Jesse Costa/WBUR)

Sanders' campaign said it had its best month of fundraising yet, taking in $25 million in January, with an average donation of $19.

"While some of our opponents have super-PACs, and some of our opponents have dozens and dozens of billionaires contributing to their campaigns, we are relying on working people of this country. That is precisely why we are going to win," he said.

While Buttigieg is building support among moderates, independents and what he calls "future former Republicans," Sanders is counting on expanding the electorate across the country with younger voters. They include bus-loads of young volunteers from out-of-state who are canvassing for him in New Hampshire. Among them, Kelly Authier from Providence, R.I., who says Sanders has the best chance of winning in November.

"We need energy — a very excited energy in order to beat Trump," Authier said. "And [Sanders] just brings out the numbers and the excitement, and that's what we're going to need in November."

Sanders is also counting on committed progressives like Andru Volinsky, a Democrat running for governor in New Hampshire, who says Sanders is the most authentic candidate around issues of economic justice. And Volinsky says flatly that he believes Buttigieg is not ready to be president.

"He's a very personable young man - but he's my son's age," Volinsky said. "He doesn't have broad experience."

In the final hours of the campaign in New Hampshire, Volinsky's point has become a harsh line of attack against Buttigieg — not from Sanders but from Biden, who finished a distant fourth in Iowa, and whose campaign badly needs a better result on Tuesday. In recent days, Biden released a tough digital ad mocking Buttigieg's mayoral record.

"Both Vice President Biden and Mayor Buttigieg have taken on tough fights," the narrator says at one point in the ad. "Under threat of a nuclear Iran, Joe Biden helped to negotiate the Iran deal. Under threat of disappearing pets, Buttigieg negotiated lighter licensing requirement on pet chip scanners."

Joe Biden poses for a photo with a young girl in his arms at a campaign rally at the Rex Theater in Manchester, NH. (Jesse Costa/WBUR)

Speaking to reporters in Manchester over the weekend, Biden said of Buttigieg, "He's no Barack Obama."

In response, Buttigieg has been trying to use Biden's attacks to his own advantage.

"Americans in small rural towns, in industrial communities, and yes, in pockets of our country's biggest cities are tired of being reduced to a punch-line by Washington politicians," Buttigieg said to a raucous gathering of New Hampshire Democrats in Manchester on Saturday. "[They're] ready for someone to take their voice to the American capital."

And on Sunday, the fight continued. Biden told ABC's This Week that Buttigieg wasn't ready to be president.

"I didn't attack him. He attacked me," Biden said.

In a subsequent interview, Buttigieg said "He's right, I'm not Barack Obama, and neither is he. Neither is anyone running for president right now. And this isn't 2008, it's 2020."

Another candidate in need of a come-back on Tuesday is Elizabeth Warren, who finished third in Iowa. She argues that she has the experience and the policies to unify the party, but has resisted direct attacks on Buttigieg or on her other opponents.

Elizabeth Warren speaks at a campaign event at Rundlett Middle School in Concord, NH. (Jesse Costa/WBUR)

"I realize that there was a lot of fighting and cross-talk at the debates, but I just really wanted to talk about — explaining to people why I am in this fight," she told WBUR. 'That seems like the better way to go here...[My campaign] is about fighting for working families. It's about fighting for our democracy. I just don't want to [make] this about shooting at other Democrats, if we can help it."

If Sanders and Buttigieg do as well on Tuesday in New Hampshire as polls suggest that they might do, the fight for Warren — and for the other Democratic candidates — will become a lot more difficult.