Given the deep unpopularity of the president and the war, that is sobering news for Republicans, even on a day they were publicly celebrating liberal Ned Lamont's win over Lieberman as proof of what they call the radicalization of the Democratic Party.

In Ohio, Republican National Chairman Ken Mehlman said the vote exposes the Democrats as the party of “isolationism, defeatism and a 'blame America first' attitude,” one that no longer has room for security-minded moderates like Lieberman.

Independent analyst Stuart Rothenberg, editor of the Rothenberg Political Report,  acknowledged that “there is some danger of an open rift” in the Democratic Party. “But for the next three months the focus is going to be on George Bush and whether people are happy with the direction of the country. November is not going to be a referendum on Ned Lamont or the Democratic Party.”

Lieberman's loss to Lamont signals that the polarization of American politics is intensifying. It proclaims a coming of age of the activist “netroots” and bloggers who now can claim their first real win and have issued a warning to any other Democrats who are seen as too cozy with the Bush White House or stray too far from party orthodoxy.

Democrats, led by Senate Minority Leader Harry Reid of Nevada and Sen. Charles Schumer of New York, chairman of the Democratic Senatorial Campaign Committee, closed ranks behind Lamont yesterday and called his victory a road map for success in the fall congressional elections.

Tuesday's voting also highlighted Bush's political vulnerability and dramatically displayed the anti-incumbent mood of voters as Lieberman was joined in defeat by incumbent House members in Michigan and Georgia.

“There is a surly mood out there,” said Charles Cook, a veteran independent political analyst in Washington. “The natives are restless and they are willing to lash out.”

Lieberman was the biggest victim. His fall from power has been precipitous: Only six years after making history as the first Jewish nominee for vice president, Lieberman stands today as the first incumbent senator in 26 years to be rejected in his party's primary.

But he was not the only victim. In Georgia, Democratic Rep. Cynthia McKinney was soundly defeated in her primary, though the reason was distinctly local – continuing embarrassment over her antics and at-times-bizarre statements. More telling was the outcome in Michigan's 7th District, where one-term Republican moderate Rep. Joe Schwarz was ousted by a conservative who hammered Schwarz for embracing Bush's immigration proposal.

“The message is you had better stick with your tribe,” said Larry Sabato, director of the University of Virginia's Center for Politics. “We have incumbents tossed out on their ear because they are insufficiently pure. So the polarization of American politics continues and accelerates.”

Democratic strategist Mark Mellman said Lieberman could not escape his reputation as Bush's favorite Democrat in Washington, a reputation hammered home in the campaign by frequent showings of a picture of the senator and president embracing and kissing at the State of the Union address.

“The activist core of the Democratic Party has been very disaffected from a party that they think has been too accommodationist and too capitulationist vis-a-vis Bush,” Mellman said. “Joe Lieberman allowed himself to become a symbol of accommodation at a time when that was an anathema to the party. That is the main lesson here. And frankly, that doesn't bode well for Bush.”

Mellman predicted only a slight effect on the party despite the anguish of party centrists in the Democratic Leadership Council, which Lieberman helped found to steer Democrats away from the left.

“There isn't going to be a civil war in the party,” he said. “What it does tell you is the antipathy to Bush is a huge motivating factor. It is true among Democrats and it is true among independents.”

John Mueller, who holds the Woody Hayes Chair of National Security Studies at Ohio State University and is an expert on public opinion in wartime, said the Connecticut outcome leaves no doubt about the direction of public opinion on Iraq.

“It confirmed the power of Iraq as an issue,” he said. “For Democrats it is really a deeply emotional issue and tied to the distrust and even hatred of George Bush.”

And for independents and a growing number of Republicans, the disaffection is strong.

“They see just no way out,” Mueller said. “It is just hopeless, a disaster, a debacle, a fiasco – whatever you want to call it – and more and more people are agreeing with that.”

Politically, that means “Republicans are going to get spanked,” Rothenberg said. “The question is how badly.”