Party activists want Reid to strip Lieberman of his chairmanship atop the Committee on Homeland Security and Government Affairs for campaigning against President-elect Barack Obama.
"He is a senior member of the Senate," Reid said on CNN's "Late Edition," reminding viewers that Lieberman would become chairman of the Armed Services or Environment and Public Works committees if "something happens to the chairman."
More personally, Reid said he "would not be majority leader but for [Lieberman's] vote."
That said, the majority leader, whose cushion is six seats larger after last Tuesday's election, said, "I recognize what he did was wrong, and quite frankly, I don’t like what he did."
Reid said he and Lieberman would continue to discuss the latter's standing in the Democratic caucus.
"I think a lot of this is very private stuff, but Joe Lieberman has done something that I think was improper," Reid said. "If we weren't on television, I'd use a stronger word of describing what he did."
Lieberman, the Democrats' vice presidential nominee in 2000, took shots at Obama and Vice President-elect Joe Biden (Del.) while campaigning for his close friend, Arizona Sen. John McCain, the Republican presidential candidate who lost last week. Democrats did not punish Lieberman at the time because they held a meager one-seat majority in the Senate last year. The Democrats' expanded majority gives Reid more power to act.