WASHINGTON (CNN) -- Independent Sen. Joe Lieberman, a former Democrat who sits with Democratic caucus, said Tuesday that he would not rule out running for re-election in 2012 as a Republican.

Lieberman angered his colleagues in the Democratic caucus this week by threatening to torpedo health care legislation if it contains a government-run public health insurance or an expansion of Medicare.

Lieberman said he wasn't sure which party, if any, he would represent in his next election.

"I like being an independent, so that's definitely a possibility," the Connecticut senator said. "But I'd say all options are open."

He called running as a Republican "unlikely" but added that he wouldn't "foreclose any possibility."

"I've reached the stage in my career where I'm not measuring every step I take based on how it's going to affect the next election," Lieberman said. "I think if you do that, you end up compromising the quality of your service."

In 2000, Lieberman was Al Gore's running mate when Democrats lost the closest presidential national election in U.S. history. Six years later, he was defeated in the Democratic primary and then ran as an independent to win re-election to the Senate.

Lieberman still sits with the Democratic caucus, which holds 60 seats in the 100-member Senate, the minimum amount necessary to overcome a filibuster.

That dynamic allowed Lieberman to assert his will in the health care debate by threatening to join a Republican filibuster if the health care bill contained the public option or Medicare expansion he opposes.

He acknowledged that his stance angered Democratic colleagues but said he acted on principle, not politics.

"I knew some of them were upset about positions I'd taken," Lieberman said. "But like each of them, I didn't get elected by telling my voters in Connecticut that I would follow the majority of my caucus even if I thought on some things they were wrong. We each have to do what we think is right."

Taking a stand in the polarized political environment means "a bunch of people will think you've done something great and a bunch of people will think you've done something awful," Lieberman said.

However, Lieberman's stance on the health care bill could prompt a backlash from liberal Democrats. He was criticized by liberal groups, and even his wife -- who formerly worked for a pharmaceutical company -- was targeted.

"I've done what I thought was right, but it's no fun to have your colleagues be angry at you," Lieberman said. "It's no fun to have your wife attacked. But, you know, you got to do what you think is right."