Former Democratic National Committee Chairman Howard Dean warned Sen. Joe Lieberman (I-Conn.) Monday that the left won't forget his role in blocking a public option during the healthcare debate should he run for reelection.

"Remember who sold you out on healthcare," Dean said at a state convention of the Connecticut AFL-CIO, according to the Connecticut Mirror. "We're not going to forget in 2012."

The early electoral threat from Dean comes even as Lieberman hasn't announced whether he'll seek another term in 2012. Earlier this month, Lieberman said he was leaning toward running for another term, but did express some hesitancy.

“The question is, at this stage in my life, do I want to do it one more time?” Lieberman said after a speech in early August.

After defeating Lieberman in a primary in 2006, businessman Ned Lamont wasn't able to beat back the Democrat-turned-Independent in the general election.

Liberal activists are certainly primed for another chance to take Lieberman out in 2012.

"I live in perpetual fear that Joe Lieberman will retire, thus depriving us the opportunity to help kick him to the curb," Daily Kos founder Markos Moulitsas wrote earlier this month. "I want his exit from politics to be as humiliating as possible."

If Democrats really hope to push Lieberman out, they may want to lay off the threats, given that the senator has often relished his role as an on-again, off-again thorn in the side of Senate Democrats.

The Democratic establishment abandoned Lieberman in favor of Lamont ahead of the 2006 general election, something Lieberman didn't exactly let go of once he made it back to the Senate as an Independent.

It still isn't clear who would run against Lieberman in 2012, but Democrats are batting around the name of Rep. Chris Murphy (D) as a potential primary challenger.