Democratic presidential candidate Bernie Sanders meets with Senate Democratic Leader Harry Reid in Reid's office on Capitol Hill, June 9, 2016. (Photo by Allison Shelley/Getty Images)

For the first time since Jan. 2, Sen. Bernie Sanders (I-Vt.) walked into the Senate to cast votes. He'd left as an unpretentious populist senator whose presidential campaign was clearly catching on; he returned with a full Secret Service detail and motorcade, with a few onlookers in the public gallery sporting brightly colored "Bernie" T-shirts.

Other than that, Sanders's re-emergence as a senator was remarkably low-key. The senator slipped into his office in the mid-afternoon, joined by his wife Jane and watched by an NBC News cameraman. Two hours later he, Jane, and the Secret Service detail entered the Capitol through a first floor door, bypassing the basement where most reporters were waiting.

"Not now, thanks," he said, when a reporter began to ask him a question.

Sanders spent the next hour making his way slowly around the Senate chamber. He cast his vote on the first of four gun safety amendments before most of his colleagues showed up, then ducked into the cloakroom. When he returned, he sat for a while with Sen. Jeff Merkley (D-Ore.), the only colleague who'd endorsed him, and the two were occasionally, happily interrupted by well-wishers of both parties, who do not expect him to end his presidential bid until next month's Democratic convention in Philadelphia.

Sen. Sherrod Brown (D-Ohio) and Sen. Al Franken (D-Minn.), two progressives who'd fended off criticism for not endorsing Sanders, gave him friendly taps on the shoulder. Sen. Charles E. Schumer (D-N.Y.) offered some celebratory finger-snaps. Sen. John McCain (R-Ariz.), the dean of the Senate's former presidential candidate club, patted Sanders on the back and stomach and told a joke inaudible from the galleries.

It was, as Senate-watchers noted, the first time all year that every senator showed up to vote. Sanders had generally escaped criticism for his truancy. The shorter no-show record of Sen. Marco Rubio (R-Fla.) became a problem for him in the Republican presidential primaries, with everyone from Donald Trump to Jeb Bush accusing Rubio of ducking his taxpayer-funded responsibility. But Hillary Clinton, who played a similar game of hooky during the 2008 primaries, never made an issue of Sanders's attendance record, and the Republicans' majority meant little of interest to Democrats needed Sanders's vote to pass or fail.

The gun-safety amendments were different. Sanders took a little heat for staying in Burlington last week instead of joining 39 Democrats in the run of floor speeches that forced today's votes. On Monday afternoon, as the vote series went on, Sanders did not join a Democratic huddle near the front of the room. Halfway through the votes, he released a statement calling the Democrats' amendments “no-brainers." (Like the rest of the Democratic caucus, he opposed the Republicans' amendments.)

“Sen. [Dianne] Feinstein’s and Sen. [Chris] Murphy’s proposals are commonsense," he said. "In light of the terrible tragedies that have taken place in Orlando and other cities, it’s not very hard to understand that terrorists or potential terrorists, criminals and the dangerously mentally ill should not have access to guns. We have got to do everything we can to stop guns from falling into the hands of people who should not have them.”

After that, and after casting a vote for Feinstein's amendment to prevent people on the terror watch list from obtaining guns, Sanders headed to a cloakroom and out the door. Jane Sanders, who had been watching the vote silently from the first row of a public gallery, headed out with him.