Like other senators leaving the chamber next month, Senator Sherrod Brown, Democrat of Ohio, on Tuesday marked the end of his three terms with an emotional, highly personal floor speech. But he refused to call it a farewell.

“It is not — I promise you — the last time you will hear from me,” Mr. Brown assured his applauding colleagues as he concluded remarks that caused him to choke up several times.

In an interview, Mr. Brown, 72, a progressive labor champion in the Senate since 2007, would not say what form his future political activism might take, raising the prospect of a potential institute on “the dignity of work” — a signature issue for him.

But he also would not rule out running for office back in Ohio or trying to return to the Senate in two years, when a special election is scheduled to be held to fill the unexpired term of JD Vance, the Republican who will resign his seat to become vice president in January.

No matter what the future holds, Mr. Brown said he intended to try to refocus his party on working-class issues.

“I’m going to stay engaged,” Mr. Brown, currently the chairman of the Banking Committee, said in the interview. “I lost. First time I’ve lost in a long, long time. I am not walking away at all from advocating for workers.”