In the wake of the Orlando massacre, a group of impassioned Senate Democrats launched a filibuster to pressure Congress on gun control. Led by Sen. Chris Murphy (D-CT), the effort to force a vote on a measure that would ban suspected terrorists from purchasing guns and expand background checks lasted more than 14 hours.

In all, more than 40 Senators, including Republican Sens. Ben Sasse (R-NE) and Pat Toomey (R-PA), joined the fight. Starting shortly after 11 a.m. Wednesday morning and lasting beyond midnight, in the end, they successfully got a vote scheduled.

But, as progressives cheered, many noticed that Sen. Bernie Sanders was missing from the fray. Sanders, who recently signaled that he would abandon his bid for the Democratic nomination, was reportedly back home in Vermont. He took to social media to show his support.

For skeptics and disillusioned supporters, it wasn’t enough.

Sanders, they noted, is still a sitting U.S. Senator. His absence stirred up a mix of disappointment and outrage, leaving many to wonder openly if Sanders had not just abandoned his colleagues in the well, but also the movement his campaign ignited. It was not difficult to wonder about its future.

Where would it make its home? What issues would be prioritized? And, if not Sanders, who would lead it? Sanders, by staying in Vermont, appeared to abdicate that role.

It isn’t unusual for a candidate to take some time off the campaign trail after a loss. Going home to Vermont must have felt right for the former mayor of leafy Burlington. Even so, with 50 dead and dozens injured in a terrorist attack on a gay nightclub in Orlando, Sanders’s decision to sit on the sidelines was a reminder that—at least on gun control—the sidelines are arguably where he has always been.

During the 2016 campaign, Hillary Clinton—the former cabinet secretary and once a senator herself—was quick to point her opponent’s legislative record on guns. In various debates, Clinton repeatedly railed about his votes against the Brady Handgun Violence Prevention Act, commonly known as the Brady Bill, and his failure to stand up to gun manufacturers in the wake of Sandy Hook—a mass shooting claimed the lives of 20 children and six adult staffers an elementary school.

Over the years, Sanders has said that rural Vermont is different from urban areas where gun violence is more rampant. His state has some of the most lenient gun laws in the country. He did not, he explained, believe his constituents should be subjected to the same gun purchasing regulations as, say, those in New York, because Vermont residents were more often game hunters.

The truth is that Sanders’s political revolution centered largely about economic disparities and paid scant attention to gun violence. His list of reforms, as enumerated on his campaign website, includes support for an assault weapons ban, and he has voted to close the gun show loophole. When accused of carrying the water of the gun lobby, Sanders quickly points out his D-minus rating with the National Rifle Association. He does not, however, support holding gun manufacturers or sellers responsible for the carnage.

“If you are a gun shop owner in Vermont and you sell somebody a gun and that person flips out and kills somebody, I don’t think it’s really fair to hold that person responsible,” Sanders told an Iowa crowd in January.

Notwithstanding his track record on gun control, his absence was curious, given that his seat in the Senate is safe. He is—by any measure—in the final stretch of a decades-long political career. It’s difficult to imagine any political strategist worth their salt advising Sanders against going to the Capitol Wednesday night. Doing so would have been political malpractice.

Sanders stands at a critical juncture. Right now, as the DNC convention looms, he and his team of advisors should be coalescing their support and deepening points of leverage if he wants establishment types and Hillary Clinton’s forces to go along with some of his proposals. As a Democrat, especially one who just mounted a campaign for the presidency, he must make sure that his colleagues know they can count on his voice and his action in the fight.

By skipping out on the filibuster on gun control, Sanders casted doubt on that. He cannot afford such questions now and neither can his movement.