"Every time I walk in there, it's amazing," he told three reporters after casting one of his final votes. "You're going to go cast a vote, and then you're on the floor having a chance to talk with all the decision-makers. It's an amazing experience."
Chiesa will be replaced Thursday by Cory Booker, who will be sworn in at noon. He won a special election Oct. 16. Booker, a Democrat, submitted his letter of resignation as Newark mayor Wednesday. It is effective starting Thursday.
Despite the 16-day shutdown that torpedoed Congress' standing with the public - and led Christie to say he would "kill myself" if he was stuck in the Senate - Chiesa, 48, spoke warmly of the institution and the lawmakers who he said found ways, at critical moments, to get deals done.
"The debates in that room were really pretty extraordinary," he said, referring to Republicans' lunch meetings. "They're passionate. Not everybody agrees, that's for sure, but they're thoughtful, people are smart, people really care about the issues that they're addressing."
Chiesa said he might run for office when his children (ages 12 and 15) are older.
"For me, it's a family issue right now," he said. "Is it something we'd think about later? Yeah. But for now, it's not something that makes sense."
He ruled out a campaign next year, when Booker will be up for reelection.
"No, unequivocally no," he said. "That is not later."
For now, Chiesa said he expects to work in private law practice in New Jersey. He planned to leave Washington after the Senate's last votes Wednesday.
He had already vacated his office in a trailer, his staff of 16 had largely moved on, and he had returned $700,000 in unspent funds to the Treasury after using $600,000, according to his staff.
Without a desk, office, or computer, Chiesa worked on an iPad in one of the extra rooms in a suite belonging to Minority Leader Mitch McConnell.
Chiesa previously was an assistant U.S. attorney, Christie's chief counsel, and then New Jersey's attorney general, but had never himself been at the political forefront.
He recalled meeting people he had only watched on television when he first arrived.
"I then was on the floor of the Senate speaking to Pat Leahy, John McCain, so that whole experience was sort of a tidal wave," he said. "And then the vice president swore me in - all on the first day."
Chiesa's biggest vote was on immigration. He supported the bipartisan Senate plan despite conservative objections.
"That proposal was better than what we had, to me, what exists now," Chiesa said.
Many pundits linked his stand to Christie, who had appointed him just weeks earlier. Chiesa saw the impact of his new job immediately. Within minutes, Coulter shared her disapproval on Twitter, something Chiesa readily recalled.
"A lot of people disagreed with my vote . . . especially Republicans," he said. But he said Christie, a close friend, never prodded him on any votes. "It's never happened," he said.
"What I thought every time is, when I go home, can I go and talk to my neighbors and my friends and make them understand why I voted the way I did?" Chiesa said.
In his brief tenure, Chiesa tried to draw attention to human trafficking, an issue he worked on in law enforcement. He led a hearing, one he proudly noted that McCain made a point to attend.
(When Chiesa was brand-new, McCain jokingly threatened to waterboard him if he did not support the immigration package.)
Chiesa reserved his warmest praise for senators who tried to find compromise. He called Sen. Orrin Hatch (R., Utah) "an inspiring figure" who was "extraordinarily generous" with his help.
He also recounted sitting in the situation room for a Syria briefing led by Biden, going to the White House to meet with President Obama during the shutdown, and meeting Chief Justice John G. Roberts Jr. and Justice Samuel A. Alito Jr.
"For any lawyer to have that chance is just remarkable," Chiesa said.
In the Senate gym, conversations were more personal.
"When you're standing there in your gym clothes . . . it's a little more informal," he said.
Personal connections, Chiesa said, are the key to breaking Washington's impasses.
"I wish that we had more interaction among the senators on some issues, because I think once we do, once people come together, issues get resolved," he said.
Around 5:30 p.m. Chiesa cast his last vote, supporting Obama's nominee to lead the Office of Personnel Management. He shook hands with other senators and chatted with Sen. Ted Cruz (R., Texas).
Chiesa recently followed Senate tradition by signing the inside of his desk, writing "Chiesa" with a Sharpie. Some colleagues took him to dinner and gave him a glass box etched with a likeness of the Senate chamber.
He refused to be drawn out on any future ties to Christie or speculation about the governor's potential 2016 run for president.
"The Christie campaign will end next Tuesday," Chiesa said, referring to the governor's race. "Whatever he chooses to do after that, I will support him in any way I can."
For now, he is looking forward to returning to Branchburg. "I have pretty good anonymity still," he said.