FARMINGTON, Conn. — The passion and energy fueling the antiwar challenge to Sen. Joseph Lieberman in Connecticut's Senate primary signals a power shift inside the Democratic Party that could reshape the politics of national security and dramatically alter the battle for the party's 2008 presidential nomination, according to strategists in both political parties.

A victory by businessman Ned Lamont on Tuesday would confirm the growing strength of the grass-roots and Internet activists who emerged in Howard Dean's presidential campaign. Driven by intense anger at President Bush and fierce opposition to the Iraq war, they are on the brink of claiming their most significant political triumph, one that would reverberate far beyond the borders here.

An upset by Lamont would affect the political calculations of Sen. Hillary Rodham Clinton, D-N.Y., who like Lieberman supported giving Bush authority to wage the Iraq war, and could excite interest in a comeback by former vice president Al Gore, who warned in 2002 that the war could be a grave strategic error. For at least the next year, any Democrat hoping to play on the 2008 stage would need to reckon with the implications of Lieberman's repudiation.

Even backers of the 2000 Democratic vice presidential nominee are now expecting this scenario. Two public polls in the past three days show Lamont with a lead of at least 10 percentage points.

While there are reasons beyond Lieberman's strong support for the war and what critics say is his accommodating stance toward Bush that have put him in trouble, the results will be read largely through the prism of what they say about Iraq and Bush's popularity.

The full ramifications of a Lieberman defeat are far from certain. One may be to signal immediate problems for Bush and the Republicans in November, but another could be to push Democrats into a more partisan, anti-war posture, a prospect that is already adding powerful new fuel to a four-year-long intraparty debate over Iraq.

Strategists say the Connecticut race has rattled the Democratic establishment, which is virtually united behind the three-term incumbent's candidacy.

"This sends a message to all Democratic officeholders," said Robert Borosage of the liberal Campaign for America's Future. "You're going to have a much tougher Democratic Party."

That could be felt most acutely by Clinton, who polls show is the early front-runner for the 2008 nomination and who has drawn criticism from the netroots activists for opposing a timetable for withdrawal. Clinton appears to have gotten the message, as she demonstrated with sharp questioning of Defense Secretary Donald Rumsfeld at a Senate hearing last Thursday.

The Connecticut race may be seen as an intensification of the partisan, polarized politics of the Bush era. Lieberman is paying a price for being an advocate of bipartisanship.

As a result, a loss Tuesday could generate more demand for a strongly anti-Bush, antiwar candidate in the Democratic primaries. Several are ready to run, including Sen. John Kerry (Mass.), former senator John Edward (N.C.) and Sen. Russell Feingold (Wis.), the only one of the three to vote against the war in 2002.

None, however, may be as attractive to the grass-roots activists as Gore. He has said he cannot conceive of circumstances that would put him in the race but may be coaxed to reconsider.

Republicans already are seeking to exploit a possible Lamont victory as a sign that Democrats are moving too far to the left on national security issues. "They want retreat — under the guise of 'reducing the U.S. footprint in Iraq,' " William Kristol writes in the latest issue of the Weekly Standard.

Sen. Christopher Dodd, D-Conn., said it is a mistake to claim, as the Republicans are doing, that the Democrats have been captured by left-wing, antiwar activists, saying. "This is really about Bush. ... It's deeper than an anti-war thing."

Still, many Democratic moderates say they see worrisome parallels to what happened to the Democrats during Vietnam, when they opposed an unpopular war but paid a price politically for years after because of a perception the party was too dovish on national security. "Candidates know they cannot appease (antiwar) activists if they are going to run winning national campaigns," said Will Marshall, president of the centrist Progressive Policy Institute. "It will intensify the tension inside the Democratic coalition as we head into two critical elections."

But leaders of the so-called netroots activists, and some party strategists, argue that Democrats stand to gain politically by aggressively challenging Bush's war policies. Parallels to Vietnam are inaccurate, they say, because of the nature of an Iraq war that now has become a low-level sectarian civil war.

"If Democrats were winning elections, that prescription would be something worth listening to," said Tom Mattzie, Washington director of, said in response to the party's moderate wing. "That's the prescription people have been giving us and we've been losing elections."

With much of the establishment backing Lieberman, Lamont initially built his campaign with the support of grass-roots activists disaffected with the incumbent and the president. Liberal bloggers around the country promoted his candidacy, helping to raise his profile, attack Lieberman and attract money (although Lamont's personal fortune has financed most of his campaign). They helped give voice to rank-and-file Democrats furious with Bush and frustrated by what they regard as cautious and ineffective party leadership in Washington and to some local elected officials angry with Lieberman.

Lieberman enjoys the support of the party's national leadership, along with most of organized labor and key constituency groups. Former President Clinton came here two weeks ago to campaign for Lieberman. Hillary Clinton has said she wants Lieberman to win. Senate Democratic leaders back his candidacy and months ago urged MoveOn officials to stay out of the primary.

If Lamont wins the primary, they will be forced to shift allegiance. Both Clintons have said they will support the winner of the primary and other party officials plan to do the same.

Lieberman, however, has said that, if he loses, he intends to run as an independent in the general election. Party officials will have to decide whether to press him to abandon those plans and, if he declines, how strongly they get behind Lamont's candidacy. Democrats hope to pick up three vulnerable Republican-held House seats in November and do not want a distracting Lieberman-Lamont general election battle to get in the way.

Rep. Rahm Emanuel, D-Ill., chairman of the Democratic Congressional Campaign Committee, said Friday he is not worried about the fallout from the Senate primary on House races, arguing that the message from Connecticut is that anyone supporting Bush's war policies is in deep trouble. "What's playing out here is that being a rubber stamp for George Bush is politically dangerous to life threatening," he said.

Republican pollster Bill McInturff sees the Connecticut Senate race as a critically important event in shaping the midterm campaigns. "This will embolden Democrats around the country," he said. "I think that this primary in its own way sets off a chain of events that makes the fall elections very quickly a debate that could be framed as a (Democratic) timeline (for withdrawing U.S. forces) versus Republicans supporting a longer term solution."

All of that may bode well for the Democrats, given sentiment about the war. As Democratic pollster Peter Hart put it: "What (Connecticut) tells us about the fall is something I think we've known all along and that is the status quo in Iraq is unacceptable. It's unacceptable to Democratic primary voters, it's unacceptable to independents and it's unacceptable to a large minority of Republicans."

Connecticut is a liberal, Democratic-leaning state, by no means a reflection of the rest of the country, which is one reason some strategists caution against reading too much into results here.

Borosage, who has battled moderates in the party for years, offered a word of caution for Democrats. Without a muscular alternative to Bush's policies, he said, "I think the debate this fall is going to be a difficult debate, even with the war unpopular."