While he didn't specifically mention the state Democrats' criticism, Lieberman acknowledged Wendesday he has "not always fit comfortably into conventional political boxes" and felt his first responsibility was to serve his constituents, state and country — not his political party.
Nancy DiNardo, the party's chairwoman, credited Lieberman with dedicating a lifetime to public service.
"His 40-year body of work is replete with Democratic successes," including his recent leadership of the repeal of the federal "don't ask, don't tell" ban on gays serving openly in the military.
The state's Republican chairman, Chris Healy, said Lieberman's "steadfast courage in defending the nation's interests" won him many Republican supporters, noting the senator's concerns about the threat Islamic fundamentalism posed to national security.
"These acts of courage and resolve almost cost Senator Lieberman his political career in 2006 when radical liberals ousted him as the candidate of the Democrat Party," Healy said.
Hours before Lieberman's plans became public on Tuesday, former Connecticut Secretary of the State Susan Bysiewicz said she would run in 2012 for Lieberman's seat.
Reps. Chris Murphy and Joe Courtney are considering a run. Republican Linda McMahon is also seen as a potential challenger, despite losing her Senate bid last year against Democrat Richard Blumenthal. Former GOP Lt. Gov. Michael Fedele's name has also been mentioned.