WASHINGTON (CNN) -- Officials with U.S. Sen. Joe Lieberman's re-election campaign say that "dirty politics" and "Rovian tactics" are to blame for what they call an online attack on their campaign Web site as Connecticut voters headed to the polls Tuesday.
The former Democratic vice presidential candidate is seeking his party's nomination for a fourth term to the Senate.
"Rovian" is a reference to White House aide and presidential political adviser Karl Rove, whom Democrats frequently have accused of unethical campaign tactics.
The Web site, http://www.joe2006.com, has been unavailable since Monday afternoon, and Lieberman campaign manager Sean Smith suggested that the campaign of senator's primary opponent, Ned Lamont, or his supporters were responsible for the disruption.
"This type of dirty politics has been a staple of the Lamont campaign from the beginning, from the nonstop personal attacks to the intimidation tactics and offensive displays to these coordinated efforts to disable our Web site," said Smith in a statement e-mailed to reporters Monday evening.
"There is no place for these Rovian tactics in Democratic politics, and we demand that our opponent calls off his supporters and their online attack dogs."
The Lamont campaign has denied any involvement.
When asked by reporters at a campaign stop Tuesday if he or his campaign was responsible for the incident, Lamont said, "No, it's just another scurrilous charge."
Liz Dupont-Diehl, a Lamont spokeswoman, told CNN that the campaign "denounced and condemned" the action, and denied any involvement by Lamont or members of his campaign. She added that the Lamont campaign did not know who was behind the incident.
The site became unavailable at some point Monday afternoon and features the message: "This account is under construction. Please check back soon. It will be available shortly. Thank you."
Various messages have appeared since Monday night in place of the Lieberman Web site, including "There is no Web site configured at this address" and "This account has been suspended. Please contact the billing/support department as soon as possible."
A CNN researcher briefly accessed the original Lieberman Web site late Monday.
Lieberman aides deny the suggestion that the Web site was taken down due to a lack of payment.
"This statement is to confirm that the suspension of displaying the Web site www.joe2006.com was not due to to an overdue account. Friends of Joe Lieberman is completely paid in full. The screen that showed yesterday is a default image from the server," the Lieberman campaign said Tuesday in a statement.
"In order to isolate where the denial of service attack was coming into the site, we disabled it as rapidly as possible. Once we were able to isolate all the site files for study, we were able to add an appropriate one-page maintenance message."