“I voted for you last year,” one man said, as he gave Pappas a firm handshake.

“I might ask you to do it again this year,” Pappas replied.

“It’s going to happen,” the man added. “I hate Trump.”

Pappas has a commanding lead in the contested Democratic primary. He also appears to be ahead, albeit by a narrower margin, in hypothetical matchups with John E. Sununu and Scott Brown, the two contenders for the Republican nomination.

Sununu, whose family is seen as a political dynasty in New Hampshire, secured President Trump’s endorsement earlier this month. That further strengthens his position in the GOP primary, though it poses a potential challenge for the general election, since Trump’s job approval rating remains underwater in New Hampshire.

While the Trump administration’s sweeping crackdown on immigrants has been a point of contention nationwide, the topic has become especially urgent in New Hampshire in recent weeks. State and local leaders have struggled to get clear answers from the federal government about plans to convert an industrial warehouse in Merrimack, N.H., into a regional processing center where US Immigration and Customs Enforcement plans to hold 400 to 600 detainees at a time, as part of a nationwide network of new detention centers.

When asked about the warehouse, Buttigieg noted that Republicans have joined in pushing back on plans for such facilities in New Hampshire and elsewhere.

“We all understand and accept the importance of proper immigration law and enforcement, but a campaign of mass incarceration and terror is not what most Americans believe is the right thing to do,” he said. “And I think the bipartisan resistance to this facility shows that.”

Pappas said he is eager to support legislation to end the partial government shutdown that’s impacting parts of the US Department of Homeland Security, but he wants to see additional guardrails on ICE, such as requiring warrants and deescalation training and ensuring officers identify themselves.

“This shouldn’t be about political leverage. It should be about getting the job done,” Pappas said. “And if we will see legislation come to the floor of the House, I want to make sure those accountability measures are in place, in addition to proper funding.”

Buttigieg said he came to New Hampshire because he is traveling around the country elevating causes and candidates worth supporting. He praised Pappas and New Hampshire in the same breath.

“I’ve seen his pragmatic style that’s very much characteristic of this state,” Buttigieg said, “and I also think he represents a welcome generational opportunity to have new voices in a more modern Senate.”

Buttigieg, 44, is popular among Democrats in New Hampshire. He finished second in the state’s presidential primary in 2020, which helped him climb from his prior job as mayor of South Bend, Ind., to a cabinet-level post overseeing the US Department of Transportation under former president Joe Biden.

His prior campaign experience was evident on Thursday, as some of the restaurant patrons regaled him with stories recalling the first time they had met him and his husband, Chasten, in 2019 at the house parties and meet-and-greet events for which the New Hampshire primary is known.

Buttigieg said campaigning in New Hampshire ahead of the 2020 primary made him a stronger candidate and influenced his views on presidential politics.

“I think it’s critically important for candidates on the national stage to have to have that experience of slowing down and talking to people in small communities, in intimate settings,” he said, “and New Hampshire is full of people who take their civic responsibility as an early state seriously.”

Looking ahead to the 2028 presidential race, Buttigieg ranks among the favorite potential candidates for likely Democratic primary voters in New Hampshire, according to early polling. Data that the University of New Hampshire Survey Center released Thursday showed Buttigieg in the lead at 20 percent, followed by Representative Alexandria Ocasio-Cortez and California Governor Gavin Newsom at 15 percent apiece, then former vice president Kamala Harris and Senator Mark Kelly at 10 percent apiece.

Andrew Smith, director of the UNH Survey Center, said Buttigieg’s activity in New Hampshire is a strong sign of his potential aspirations to launch another presidential bid. If that’s the case, then stumping alongside Pappas and others is a good opportunity to build connections and support among the politically engaged Granite Staters who would be interested in working for the 2028 campaign, he said.

Smith said the latest data on potential Republican candidates show Vice President JD Vance is the clear front-runner for the GOP’s 2028 primary in New Hampshire, which signals Vance is also well-positioned to win his party’s nomination. But there is no front-runner in the Democratic contest.

“There’s no clear leader here,” Smith said. “There is an open field.”

Buttigieg is far from the only potential presidential hopeful making noteworthy visits to New Hampshire. Newsom and Kentucky Governor Andy Beshear are each expected to visit in early March, and several others — including Illinois Governor JB Pritzker and senators Cory Booker, Amy Klobuchar, and Ruben Gallego — have made similar treks in recent months.

After visiting with Pappas in Manchester on Thursday afternoon, Buttigieg attended a community conversation Thursday evening with Representative Maggie Goodlander in Nashua. He’s expected to join local leaders in Concord on Friday morning, then deliver a speech at Dartmouth College on Friday evening, before joining local organizers for an event on Saturday.

Steven Porter can be reached at steven.porter@globe.com. Follow him @reporterporter.