HARTFORD, Conn. (AP) – Democratic Sen. Joe Lieberman, who was locked in a battle with an anti-war challenger in the nation’s most closely watched primary race Tuesday, accused his opponent’s supporters of hacking his campaign Web site and e-mail system.

Lieberman campaign manager Sean Smith said the campaign has contacted the Connecticut attorney general’s office and asked for a criminal investigation by state and federal authorities.

Lieberman, campaigning Tuesday in New Haven, said he has no proof that Lamont supporters are responsible, but is asking state party chairman to intervene.

“I’m concerned that our Web site is knocked out on the day of the primary, you’d assume it wasn’t any casual observer,” Lieberman said.

Lamont, campaigning early Tuesday afternoon in Bridgeport called the accusation “just another scurrilous charge.” His campaign denied involvement and said the primary day accusation is a sign of Lieberman’s desperation.

A spokesman for the U.S. Attorney’s office declined immediate comment. Calls placed to the FBI and the chief state’s attorney’s office seeking comment were not immediately returned.

Smith said the site began having problems Monday night and crashed for good at 7 a.m.

“Voters cannot go to our Web site. They cannot access information,” Smith said. “It is a deliberate attempt to disenfranchise voters.”

Recent polls showed Lamont with a lead but Lieberman closing the gap in recent days. If defeated, Lieberman would be only the fourth incumbent senator since 1980 to lose a primary election. The three-term senator, nationally known for his centrist views, has endured harsh criticism in his home state for supporting the Iraq war and has been labeled by some Democrats as too close to Republicans and President Bush.

The race has attracted tremendous interest, both in Connecticut and nationally. More than 14,000 Connecticut voters switched their registration from unaffiliated to Democrat to vote in the primary, while another 14,000 new voters registered as Democrats, according to state statistics.

Secretary of the State Susan Bysiewicz projected turnout between 45 percent and 50 percent, much higher than the 25 percent turnout that is typical of state primaries. She said many communities had reported turnout greater than 20 percent by 1 p.m., and poll workers were expecting the heaviest turnout in the late afternoon, as people went home from work.

“I’m completely for Lamont because of the war issue,” said William Clement, 57, who voted in Hartford’s west end Tuesday morning. “I’m totally disgusted with Lieberman and his positions. I think he sold us out.”

Norwich’s Raymond Deauchemn, 55, said he voted for Lamont. “I don’t think Lieberman is doing that great of a job. He’s more like Bush than anything else. I think he’s his little puppet.”

Hartford resident Jack Ellovich of Hartford cast his vote Tuesday morning for Lieberman, although he said his wife voted for Lamont.

“He’s got the experience, he’s got the clout,” said Ellovich of Lieberman. “He’s already got the standing in the Senate. I think he can get stuff done for Connecticut and I don’t think Lamont really knows how the system works.”

Lieberman has campaigned with the support of party leaders in Washington and at home. But a defeat would strip him of that backing as early as Tuesday night or Wednesday, and he likely would come under to pressure from longtime allies to abandon plans to run as an independent this fall.

Mike Pohl, 43, secretary of the Democratic Town Committee in Manchester, said he was leaning toward Lieberman because a three-way battle in the general election would hurt the party.

“If Lieberman won this primary it would be over tomorrow,” he said. “If Lamont wins it’s not over.”

But Terry Bogli, 60, said she voted for Lamont.

“We have to go with what’s in here,” she said, pointing to her heart. “Sometimes you have to not be afraid of that battle.”

Lamont, a millionaire owner of a cable television company, held a slight lead of 51 percent to 45 percent over Lieberman among likely Democratic voters heading into Tuesday’s primary. The Quinnipiac University telephone poll of 784 likely Democratic primary voters, conducted from July 31 to Aug. 6, has a sampling error margin of plus or minus 3.5 percentage points.

The race has tightened in recent days, with Lamont’s lead cut from 13 points.

Lieberman said he believes voters are coming back to him.

“I feel they were flirting with the other guy for a while, wanting to send me a message,” he said Monday during a stop at a restaurant in Hartford. “I got their message. I think they want to send me back to Washington to continue working with them, fighting for them, and delivering for Connecticut.”

Quinnipiac Poll Director Douglas Schwartz said people may be having second thoughts about Lamont, whose only political experience is two years as a Greenwich selectman and six years on the town’s Board of Estimate and Taxation.

Lamont, who was to campaign Tuesday in Greenwich, Bridgeport, New Haven and Hartford, told Hartford television station WTIC that he expected to win and send a message about the need to pull out of Iraq.

“I think we’ve got a good competitive race here,” he said Monday, adding that recent polls are “little narrow samples” and that “everybody knows they bounce up and down.”

Many of Lamont’s supporters see the race as a chance to take down an incumbent senator and assume a bigger role in the Democratic party.

Lieberman has tried to persuade voters that he is still a true Democrat and says Lamont will need “training wheels” should he ultimately win the general election.

Should Lieberman lose Tuesday, supporters would have until Wednesday afternoon to submit petitions to put Lieberman’s name on the ballot as an independent.