Senator Robert Menendez of New Jersey made a defiant and impassioned speech to his fellow Senate Democrats on Thursday, maintaining his innocence and repeating that he had no intention of stepping down after being indicted on bribery charges, despite calls from many of his colleagues to do so.

Mr. Menendez’s obstinate address at a closed-door luncheon in the Capitol followed appeals by more than half of the Senate Democrats, including the head of their campaign arm, for him to resign. It prompted one of his Democratic colleagues, Senator John Fetterman of Pennsylvania, to float the idea of forcing him to leave office.

“Now that it’s confirmed that he’s not going to go the honorable way, I would like to pursue whatever avenues are available,” Mr. Fetterman told reporters on Thursday, after being asked whether he would seek to file a resolution to expel Mr. Menendez from the Senate. “If that is an option, absolutely, I would pursue that.”

Mr. Fetterman, who was the first senator to call on Mr. Menendez to step down, did not attend the session in which the New Jersey Democrat addressed his colleagues, arguing that he had no interest in hearing what Mr. Menendez had to say unless he was planning to announce his resignation. Mr. Fetterman added that he hoped Senator Chuck Schumer, Democrat of New York and the majority leader, would ask Mr. Menendez to step down.

“I’m not in a position to tell him what he should do, but I hope he does,” Mr. Fetterman said. “And I hope the rest of our caucus and the Republicans join the rest of us that have already made the right call.”

Any senator can file a resolution to expel a member of the body, but two-thirds of the Senate — 67 votes — is required to eject any member. In the history of the Senate, the maneuver has only been used to oust 15 senators, almost all of them during the Civil War for supporting the Confederate rebellion. No senator has been expelled since 1862, though some facing the threat of expulsion have resigned.

Thus far, it does not appear there would be enough votes in the Senate to support a measure to oust him. Republicans have either demurred in their opinions about Mr. Menendez’s tenure or said that his fate is a matter for the voters of New Jersey to decide.

Some influential Democrats have also refused to condemn him.

“Basically the whole theme of everything was, every American is innocent until proven guilty, give him the benefit of the doubt, let him defend himself,” Senator Joe Manchin III, Democrat of West Virginia, told reporters after Mr. Menendez’s address. Mr. Manchin is among the Democrats who have declined to join the chorus of those calling on him to step down.

Mr. Schumer, who also has not called on Mr. Menendez to resign, did not comment on his speech during the gathering, Mr. Manchin told reporters. While Mr. Menendez invited his colleagues to ask questions, none did.

Few senators who heard Mr. Menendez out were willing to talk to reporters afterward, but the mood as they emerged from the luncheon appeared tense. At least one Senate Democratic aide speculated that by addressing his fellow senators, Mr. Menendez had opened them all to potential questioning by prosecutors in his case.

Mr. Menendez pleaded not guilty to bribery charges on Wednesday before a federal judge in Manhattan, and he has not addressed reporters at the Capitol since returning to Washington. His closed-door appeal to Senate Democrats was scheduled at his request.

Senators Chris Coons of Delaware, Brian Schatz of Hawaii and Jeanne Shaheen of New Hampshire, the three Democratic members of the Senate Ethics Committee, voluntarily left the room before Mr. Menendez spoke, according to Mr. Coons.

“As the chairman of the Ethics Committee, I can’t comment on any matter that is or may be before the committee,” he told reporters. “As a result, I do my best to avoid circumstances where matters that are or may be before the Ethics Committee are discussed.”