Updated: 6:56 p.m.c

Sen. Joe Lieberman (I-Conn.) is not expected to seek a fifth Senate term in 2012, according to multiple news reports late Tuesday afternoon.

Confirmation is expected to come at a Wednesday afternoon press conference in Stamford, Conn. His staff was publicly tight-lipped about Lieberman’s intentions, except to say “the decision has been made for a while.”

The news, posted online by a Hartford Courant columnist and the New London Day, among other media outlets, comes the same day the Democratic field in the race started taking shape. Former Connecticut Secretary of State Susan Bysiewicz (D) announced her candidacy Tuesday morning, and Rep. Christopher Murphy (D) could be close behind.

“My interest in running for Senate in 2012 is well known in the state, and I expect to announce my decision very soon,” Murphy said in a statement provided to Roll Call in the early afternoon.

Lieberman, 68, an Independent who caucuses with Democrats, has been noncommittal thus far when asked about his re-election plans. While he recently said he was leaning toward running for his fifth term as an Independent, his office did not dispute the media reports of his looming retirement when asked Tuesday.

The National Republican Senatorial Committee wasted little time in highlighting the fact that the Lieberman news came just hours after Sen. Kent Conrad (D-N.D.) announced he will retire in 2012, becoming the first Democrat to do so.

“With yet a second member of the Senate Democrat caucus preparing for retirement within a 24-hour period, all of us are left to wonder how many more Democrats may follow in their footsteps,” NRSC Communications Director Brian Walsh said.

Democrats are defending 23 seats in 2012, while Republicans are defending only 10 — most of which are considered to be in safe territory.