Democratic vice-presidential candidate has had long career, having been Al Gore's running mate in 2000 election

This article is more than 9 years old

This article is more than 9 years old

Former Democratic vice-presidential candidate Joe Lieberman, one of the most familiar faces on the American political scene, has announced he will not seek re-election to the Senate in 2012. The move puts paid to a long and varied political career that has spanned four terms in the upper house of Congress.

The period has seen Lieberman, 68, move from being Al Gore's running mate in the 2000 presidential election to standing as an independent senator after falling out with Democrats over the Iraq war. The development is expected to be officially announced today but broke over various news outlets a day ahead of time.

It was accompanied by speculation that Lieberman – who has become increasingly unpopular with centrists and Democrats in his home state of Connecticut – did not want to lose at the ballot box in the next election.

"I don't think he wanted to go out feet first," a source familiar with the decision told the New York Times.

Lieberman has certainly grown more and more conservative in recent years.

He was ousted in a 2006 Democratic Senate primary over his pro-war stance but stood by himself as head of his own party and won back his seat.

Although he generally sides with the Democrats in the Senate, he also campaigned on behalf of Republican John McCain in the 2008 election against the current occupant of the White House, President Barack Obama.

Late last year the non-partisan Public Policy Polling group put Lieberman's statewide approval in Connecticut at just 33% , with 54% of voters disapproving of him.

However, he had won plaudits from many of his former supporters in recent weeks for championing gay rights via the repeal of the "Don't Ask, Don't Tell'" ban on gay people serving openly in the military.