Democrat voters in Connecticut have sent a pointed message to their party leaders about their impatience with the Iraq war by rejecting their veteran senator Joe Lieberman in the state's Democratic primary election.

Mr Lieberman has had a distinguished political career, climaxing when he was Al Gore's running mate in the 2000 presidential race, but his support - albeit critical - for the invasion and occupation of Iraq have fallen out of tune with popular opinion amongst his core voters at home.

Yesterday the affluent, socially conservative Democrat electorate of Connecticut, a corner of New England that is America's richest state, turned out in large numbers to support Ned Lamont, a political novice who ran a negative campaign attacking the Iraq war.

Mr Lieberman rang his rival, the millionaire owner of a cable television company, at 11pm (4am BST) to congratulate him on his victory.

In a speech to supporters in Hartford, the state capital, he then pledged to fight back, running as an independent Democrat candidate without the full support of the party machine in the general election this autumn.

"As I see it, in this campaign, we've just finished the first half and the Lamont team is ahead - but in the second half, our team, Team Connecticut, is going to surge forward to victory in November," said Mr Lieberman, to cheers.

"For the sake of our state, our country and my party, I cannot, I will not let this result stand."

He criticised his rival's campaign, accusing Mr Lamont of dealing in insults and 'partisan polarising' by blaming Mr Lieberman for President Bush's handling of Iraq.

The Lamont campaign had played and replayed video of the kiss that President Bush planted on Lieberman’s cheek after the 2005 State of the Union address.

There were also allegations of dirty tricks. On the final day of the race, Mr Lieberman accused his opponent’s supporters of hacking his campaign website and e-mail system, crashing both at 7am on the morning of the poll.

Mr Lamont brushed the accusations aside as scurrilous. In his victory speech, he jubilantly told his backers: "They call Connecticut the land of steady habits. Tonight we voted for a big change."

Some were pointing to a wider political significance to the result. Avi Green, a volunteer from Boston, commented: "People are going to look back and say the Bush years started to end in Connecticut. The Republicans are going to look at tonight and realise there’s blood in the water."

The Connecticut Senate race has dominated America's political landscape in recent weeks, as the support for Mr Lamont demonstrated the power of anti-war sentiment among Democrats.

It was a race watched closely by the liberal, internet-savvy Democrats who lead the party’s emerging "netroots" movement, groups such as Moveon.org that played a big role in pushing Mr Lamont’s candidacy.

Officials said that turnout was up to 50 per cent when primaries usually only draw 25 percent of voters. Vote totals showed roughly 16,000 more ballots cast for the Democratic Senate primary than the party primary for governor, reflecting the extra attention to the Lieberman-Lamont battle.

As a result, Mr Lieberman's decision not to take defeat lying down but to run as an independent Democrat candidate may not please his party leadership. Harry Reid, the Senate minority leader, had been planning to call on the party to unite around the victorious Mr Lamont this morning.

Now the Democrat hierarchy must decide whether to approach Mr Lieberman in private and ask him to back off, while it reconsiders its own general position on the Iraq war.

"The big question is if they will approach Joe about dropping out, because they don't want to get his back up against the wall," a senior party aide told The New York Times.

Elsewhere, in the southern state of Georgia, Cynthia McKinney, a fiery black congresswoman with a reputation for controversy, lost a runoff for the Democratic nomination to Hank Johnson, the black former commissioner of DeKalb County, 58 per cent to 41 per cent.

Ms McKinney once suggested that the Bush Administration had advance knowledge of the September 11 terror attacks - remarks that resulted in her losing her seat in 2002. She won it back two years later.

In March she was in the news again when she struck a Capitol police officer who did not recognise her and tried to stop her from entering a House office building. A grand jury in Washington declined to indict her, but she was forced to apologise before the House.

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