NED LAMONT has floppy hair, talks too fast and has inherited a fortune from a blue-chip Republican family of Wall Street financiers. He may be an unlikely and unprepossessing figurehead of the new American Left but he is nonetheless giving the Democratic Party establishment palpitations.

The Greenwich-based businessman is mounting a ferocious challenge to three-term Connecticut senator Joe Lieberman for the party’s nomination in a primary election. Opinion polls show him closing rapidly on the incumbent, who has been sufficiently spooked to announce this week that he will stand as an Independent if he loses on August 8.

Propelling Mr Lamont forward is a vocal army of anti-war internet activists who have been infuriated by Mr Lieberman’s support for President Bush over Iraq and what they have portrayed as his cosiness with Republicans on other issues.

The Democratic leadership is deeply uneasy about this contest. Not only does it threaten to end the 36-year career of one of its biggest beasts in Washington but Mr Lamont’s challenge is also turning the spotlight on the party’s divisions at a time when Democrats should be presenting a united front for mid-term elections in which they have a good chance of taking control of one — or both — houses of Congress.

Even more disturbing for them is the prospect of the Connecticut primary becoming a model for the presidential primary elections in 2008. Howard Dean got close to winning the nomination last time with the help of the anti-war vote and the subsequent fall-out did much to cloud John Kerry’s campaign. If the Internet activists can take out Mr Lieberman, they could yet wreak havoc with the presidential ambitions of Hillary Clinton, who has also failed to renounce her support for the war.

Mrs Clinton was swift this week to declare that she would not support Mr Lieberman if he ran as an independent and, in a nod to the party’s liberal base, added: “I believe in the Democratic Party and I believe we must honour the decisions made by Democratic voters.”

Mr Lieberman, who only six years ago was Al Gore’s running mate, told The Times that he was being unfairly singled out. “A lot of other Democrats have a similar position to me on Iraq, but this has become a cause celebre — I’ve no idea why.”

His opponents’ answer to that is pinned to many of their lapels. They have produced a campaign badge showing Mr Lieberman and George Bush embracing after the president’s 2005 State of the Union address, along with the message: “The kiss: too close for comfort.” The Senator initially tried to make light of it, saying that at least he had not kissed Mr Bush back. Now he denies there was any lip contact at all, but admits to getting little hug while the president whispered: “Thank you for being a patriotic American.”

Mr Lieberman thinks his troubles are partly a consequence of what he calls the “rigidly, reflexively partisan” atmosphere in Washington. Democrats are under more pressure than ever to stand up to the administration but he insists on seeking common ground.

This has helped sustain his popularity among the wider electorate in Connecticut but does not do him much good when he needs the support of the Democratic selectorate on August 8 — when soft supporters are on holiday and only the activists are certain to vote.

For them, Iraq is the number one issue and Mr Lamont has been ruthlessly tapping into their anger. In a televised debate on Thursday the two clashed repeatedly on the issue.

Although Mr Lieberman accused his challenger of “flip-flopping” on how and when to withdraw troops, Mr Lamont declared he “absolutely” supported setting a deadline for bringing US soldiers home — a view shared only by a minority of Democratic Senators. Mr Lieberman is among only six who voted against beginning to pull troops out at all.

In an interview in his Greenwich offices yesterday, Mr Lamont said the Senator had not only been a “cheerleader for war” but had gone “out of his way to question the integrity and even the patriotism” of Democrats who urge a different course.

THE PRIMARY

Primaries and caucuses to choose the next Democratic presidential candidate begin in 2008

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