Democrats and Republicans here are locked in a legal battle over GOP operatives who tried to suppress voter turnout in a key 2002 U.S. Senate race by jamming Democratic get-out-the-vote phone banks on Election Day.

New Hampshire Democrats, through a civil lawsuit, are trying to question Ken Mehlman, the chairman of the Republican National Committee, and White House officials about why one GOP official who was involved in the scheme called the White House repeatedly.

Democrats describe the phone-jamming case in Nixonian terms, using Watergate-era phrases such as ''follow the money'' and ''what did they know and when did they know it?''

''It's been the gift that's kept on giving for the Democrats,'' said Dante Scala, a political-science professor at Manchester's St. Anselm College. ''It's been gradually going up the ladder, and now it's in Ken Mehlman's office.''

Democrats say smoking guns abound in the case:

l A Republican operative who later was convicted in the case called Mehlman's former office in the White House nearly two dozen times.

l The RNC paid millions of dollars in legal expenses for the operative; it was under no legal obligation to do so.

l Contributions were made to the state GOP by Indian tribes whom disgraced lobbyist Jack Abramoff represented and by former House Speaker Tom DeLay's political action committee in amounts that together almost equaled the cost of the phone-jamming scheme.

Republican officials are on the defensive. They call the vote-suppression scheme an unfortunate incident that was the work of rogue operatives who did it without party leaders' knowledge. They say the civil suit is a baseless attempt by Democrats to score points and ruin the New Hampshire Republican Party financially. State GOP officials filed a countersuit charging that the state Democratic Party had ''ulterior and improper'' motives in suing them.

''This is taking a local political issue and exploiting it to the national level,'' Ovide Lamontagne, the New Hampshire GOP's attorney, said of the Democratic lawsuit. ''They are not interested in justice.''

There's no argument about the basic facts: On Nov. 5, 2002, hot lines that state Democrats and a firefighter's association had set up to urge people to the polls were jammed by more than 800 hang-up calls. State Republican officials say that once they learned of the scheme, they tried to stop it. The jamming occurred during what was billed as a hotly contested Senate race between Republican John Sununu, who was then a member of the House of Representatives, and Democrat Jeanne Shaheen, then New Hampshire's governor. Party control of the Senate was thought to possibly turn on the outcome.

In the end, the race wasn't close. Sununu defeated Shaheen by about 20,000 votes, weakening Democratic arguments that the suppression scheme cost them the election.

Three men have been convicted:

l James Tobin, 45, who headed the Republican National Committee's New England efforts in 2002 and who was the regional director for President Bush's 2004 re-election campaign. He was convicted in December of one count of aiding and abetting telephone harassment and one count of conspiracy to commit telephone harassment. He faces up to seven years in prison for both felonies. He's scheduled to be sentenced in May.

l Chuck McGee, former executive director of the state Republican Party, pleaded guilty to hatching the scheme and served seven months in prison.

l Allen Raymond, former president of GOP Marketplace LLC, a Virginia-based company, pleaded guilty to helping to execute the plan and is serving a three-month sentence.

Last month, a federal grand jury indicted a fourth man, Shaun Hansen, 34, of Spokane Wash., and charged him with the same crimes as Tobin. Prosecutors say that Hansen, former co-owner of an Idaho-based telemarketing company, was paid $2,500 to have his employees place hundreds of hang-up calls to disrupt the New Hampshire get-out-the-vote effort.

Hansen pleaded not guilty. But he told the Idaho State Journal in July 2004 that GOP Marketplace hired his company to call six phone lines that the New Hampshire Democratic Party and the firefighter's association used. He said he didn't know the reason for the calls.

Democrats say the case has gotten more and more curious as it has gone along. They noticed that Tobin had high-powered legal representation and later learned that the RNC was paying the bills.

RNC Chairman Mehlman said in CNN interviews this month that the decision to pay for Tobin's lawyers was made before he became the chairman, and he defended the payments, maintaining ''it was right to honor the decision.''

Throughout the controversy, state GOP officials maintained that Tobin and McGee acted on their own. Mehlman says the national party had nothing to do with the scheme.

Fuel was added to the fire after the Senate Majority Project, a Democratic activist group, found records from Tobin's trial detailing 22 telephone calls that he placed from New Hampshire to the White House political office - which Mehlman headed at the time - on Nov. 5 and 6.

In addition to the legal bills, state Democrats say they've found another curious national GOP link to the scheme: $15,000 in contributions to the state Republican Party from two of Abramoff's Indian tribe clients and from Americans for a Republican Majority, a DeLay-led political action committee, about a week before the election.

Democrats have taken all these circumstantial links and run with them. Sens. Edward Kennedy, D-Mass., and Patrick Leahy, D-Vt., fired off a letter to Attorney General Alberto Gonzales on April 20 asking whether the Justice Department is looking into it.

Howard Dean, the Democratic National Committee chairman, has hawked the New Hampshire story on TV news shows. He also sent a letter to Mehlman earlier this month asking whether the White House authorized the phone-jamming.