"I have a parliamentary inquiry!" Sanders shouted on the Senate floor one night last week, testing the patience of his colleagues, who were eager to leave the Capitol and start their holiday break.
But just off the Senate floor and across the Capitol, one vestige of his presidential campaign remains: his Secret Service detail. And taxpayers are footing the bill.
Protecting a presidential candidate costs about $40,000 a day, a federal official familiar with the Homeland Security budget told CNN. For Sanders, that's more than a half-million dollars since the last primary on June 14. The cost could grow by nearly $2 million if he stays in the race through the Democratic convention in Philadelphia later.
The federal official said it's difficult to tally exact costs, since some agents are working on other projects simultaneously, but the overall amount spent on Sanders is far higher when calculating the weeks of protection he received after the nomination was effectively out of his reach, as Hillary Clinton surpassed him in the delegate count.
Sanders waved off questions on the matter.
"I think security is probably something we shouldn't be talking about too much," Sanders told CNN last week, walking with his protective detail through the halls of the Senate office buildings.
But many of his fellow senators are talking about it. Several told CNN privately they were stunned to see Sanders at the Capitol with such an entourage, particularly because the building is already secured by U.S. Capitol Police. One colleague, who declined to be identified to avoid publicly talking ill of a fellow senator, bluntly said: "Bernie's on an ego kick."
The Secret Service is also stretched thin, preparing for two additional high-profile protectees as both parties are preparing to announce their vice presidential candidates in July.
A spokesman for Sanders declined to discuss why the senator has not relinquished his Secret Service protection and his around-the-clock coverage in Washington, at home in Vermont or wherever he goes.
Sen. Ron Johnson, chairman of the Homeland Security Committee, told CNN that active presidential candidates should be protected. He stopped short of sharply criticizing Sanders, but said he hoped it would be resolved soon.
"At some point in time, hopefully Senator Sanders will realize he's not going to be the nominee of the Democratic Party and Secret Service protection can be removed," Johnson, R-Wisconsin, said.
Asked whether it was a wise use of taxpayer money, Johnson said: "That's going to be up to Sen. Sanders."
Sanders started receiving Secret Service coverage in February, between the Iowa caucuses and the New Hampshire primary, as his candidacy soared and his crowds swelled. He had several close calls with protestors along the way, where his agents rushed in to protect him from potential harm.
A spokeswoman for the Secret Service declined to comment on the duration or cost of Sanders' protection.
Department guidelines say a candidate loses coverage when he or she formally drops out of the race or suspend their campaign. Unless Sanders does that, his armed detail will likely surround him until Clinton is formally nominated at the Democratic convention in Philadelphia in late July.
Sanders has acknowledged he won't be the nominee and has said he will likely vote for Clinton, but advisers say he is keeping his candidacy alive to influence the party platform at the convention.
The Secret Service is stretched particularly thin during a presidential campaign and Sanders' decision not to suspend his campaign has raised some eyebrows inside the agency. Many believe his coverage would end after the District of Columbia primary ended the voting season June 14.
"We protect candidates and I don't really think he can be defined as a candidate at this point," said a person involved in Secret Service protection, speaking on condition of anonymity, adding that Sanders' decision seemed "unprecedented."
On Capitol Hill, Sanders' small motorcade turned heads last week, particularly when many rank-and-file senators drive themselves or hop into the front seat of an aide's car after votes are finished for the night. Only congressional leaders receive a protective detail and transportation.
Several Democratic senators told CNN they didn't feel comfortable discussing Sanders' security. But politically speaking, they said it was time for Sanders to step aside.
"I love Bernie. He's a good senator and he has certainly contributed in this presidential campaign," said Sen. Bill Nelson, D-Florida. "But it is now time for him to stand down."