DURHAM, N.H. — Democratic presidential nominee Hillary Clinton wasn’t subtle about the reason she returned Wednesday to this state for the first time in months. She wants — and needs — younger voters to be more excited about her campaign.

The location: University of New Hampshire. The topic: Her proposal for free tuition at public colleges for some families. Her costar: Senator Bernie Sanders, who won 83 percent of younger voters in February’s Democratic primary in the state.

Many in the student-heavy crowd were ardent Sanders supporters in the primary, and some of them remained skeptical of Clinton’s candidacy. It’s a lingering issue for her campaign: As national polls show Clinton in an increasingly competitive race, some young voters are gravitating toward third-party candidates, including the Libertarian nominee, Gary Johnson, who appeared on campus hours later for a televised town hall.

“Bernie’s campaign energized so many young people,’’ Clinton told the crowd at the school’s indoor track facility. “And there are no Americans who have more at stake in this election because so much of what will happen will affect your lives and your jobs and our country, our future, and what kind of a world we want to build together.’’

Clinton spoke about her proposal that would make public colleges or universities free for households with an income of $125,000 or less. The topic is particularly relevant in New Hampshire: Studies show college graduates in the state have among the highest student debt load in the country — more than $33,000 on average — according to data compiled by the Institute for College Access and Success.

“Paying for college shouldn’t be so hard that it prevents you from getting your education,’’ Clinton said. “None of this will happen if you all don’t turn out and vote.

She frequently cited Sanders, praising the Vermonter and calling her former primary rival a “friend.’’ In turn, Sanders, who endorsed Clinton in July during her last appearance in the state, urged the audience of about 1,200 people to support her.

“All of you know this is a very tight election and that New Hampshire could decide the outcome,’’ Sanders said. “So I am asking you here today not only to vote for Secretary Clinton, but to work to get your uncles and your aunts and to get your friends to vote.’’

Among those Sanders hopes to convince is Sarah King-Mayes, a UNH sophomore who was a lead organizer for his campaign on campus.

“I am sort of in a weird spot, like a lot of Bernie supporters I know,’’ said King-Mayes. “I really dislike Hillary and hoped that others would get in the debates. But unless Gary Johnson blows up and gains support, I guess I will have to vote for Hillary.

“Even those I know who are backing Hillary aren’t putting in as much effort for her as they did for Sanders,’’ she said.

Not all of Sanders’ supporters at the state’s largest college have such a mixed take.

Doug Marino, another core member of the Sanders campaign at UNH, said he had no problem eventually backing Clinton.

“The enthusiasm is growing for her every day on campus as people are starting to tune in to the race,’’ Marino said.

In the most recent poll of New Hampshire, from Monmouth University, Clinton led Donald Trump, 47 percent to 38 percent, and Johnson received 10 percent. The survey also found Johnson is more popular with younger voters than with any other group, said Patrick Murray, director of the Monmouth University Polling Institute.

“Johnson is getting higher support in New Hampshire than he is in a lot of the other states that we are polling,’’ Murray said.

Overall, recent polls have shown a tightening race in New Hampshire and other swing states. Clinton still holds, on average, a five-point lead over Trump. The race is closer in other states, including next door in Maine, where a Portland Press Herald/Maine Sunday Telegram poll from this weekend showed the statewide contest to be statistically tied.

Yet New Hampshire is receiving a lot of attention this week from the presidential campaigns. In addition to Clinton and Johnson, Trump is scheduled to host a rally in Bedford Thursday. Trump’s running mate, Governor Mike Pence of Indiana, held a rally in Milford on Monday.

Prior to the event, Clinton had lunch in Durham with a fund-raising contest winner. On Wednesday night, she was scheduled to attend a fund-raiser at the Fairmont Copley Plaza Hotel in Boston, which included a live performance from pop singer Sara Bareilles.

Jim O’Sullivan of the Globe staff contributed to this report. James Pindell can be reached at james.pindell@globe.com. Follow him on Twitter @jamespindell or subscribe to his daily e-mail update on the 2016 campaign at www.bostonglobe.com/ground game.