Former Virginia Gov. Mark R. Warner is being courted by national Democrats to run for the U.S. Senate seat now held by John W. Warner (R-Va.) and is seriously considering the 2008 challenge, several Capitol Hill and state sources said.

Mark Warner had dinner with Democratic Senatorial Campaign Committee Chairman Charles E. Schumer (N.Y.) last month, and the two have since talked regularly about the contest, said the sources, who spoke on condition of anonymity because a final decision has not been made.

Mark Warner, 52, has said in the past that he would consider a Senate bid only if the seat were vacant. But he is not ruling out a bid even if John Warner, a five-term incumbent and friend of the former governor, runs for reelection, the sources said.

If both Warners run, it would pit two of the commonwealth's most popular political figures against each other in a rematch of their 1996 U.S. Senate race.

"Governor Warner plans to stay engaged in the public policy debate and has not ruled out running for elected office again, either for the U.S. Senate or for governor," said Monica Dixon, executive director of Warner's Forward Together political action committee. Warner was out of the country and unreachable for comment.

John Warner, who just turned 80 and has not announced whether he will run for a sixth term, said he would not be deterred by a challenge from his onetime opponent.

"I welcome any contender that wants to come," the senator said when told of the former governor's consideration of a rematch. "Been there, done that. I fear no one."

However, some doubt John Warner's commitment to run. One Republican active in Virginia politics said that Warner has told U.S. Rep. Thomas M. Davis III (R-Va.) to prepare to run if the senator decides against another bid. "Davis is actively calling people and is saying on the calls that he has been told by Warner to get ready," the source said.

Davis did not return a call seeking comment. The senator said only that Davis is "a very, very fine and competent public servant."

Mark and John Warner faced each other in 1996 in a mostly polite but sometimes confusing contest. To reach voters, the Democrat offered a simple slogan on bumper stickers: "MARKNOTJOHN."

Mark Warner lost the race by 5 percentage points and later joked about it in speeches, saying that he won the silver medal in his political debut. He returned to politics five years later in his successful 2001 campaign for governor, defeating Republican Mark L. Earley.

In Virginia, the two major parties have grown increasingly competitive since Warner won that race. Although President Bush carried the state with 54 percent of the vote in 2004, Gov. Timothy M. Kaine (D) claimed the governor's mansion in 2005, and Sen. James Webb (D) toppled George Allen (R) in November. In an interview in December, John Warner said he needed to consider those results as he weighed another run.

Mark Warner left office in 2005 with approval ratings of more than 80 percent and quickly began considering a possible run for the presidency. He formed Forward Together, hired employees with national experience and traveled the country to gain support for a likely bid. Then, last fall, he abruptly dropped out of a race he had never entered, citing concerns about the impact that a campaign would have on his wife and three daughters.

Mark Warner's friends and political allies say that at times he regrets leaving the presidential race and wants to get back into public life. A second term as governor seemed the more likely option for him, and he regularly expressed regret while campaigning for Kaine that the state constitution would not allow him to serve a second consecutive term.

But with the next governor's race not until 2009, Warner is at least mulling over the possibility of a run for Senate under the regular and repeated urgings of Schumer.

"Mark Warner is one of the most accomplished and respected public servants in Virginia," said Matt Miller, communications director of the Democratic Senatorial Campaign Committee. "We think he would be an excellent candidate for the Senate, and we will continue to talk with him about it."

The biggest obstacle to a Mark Warner candidacy could well be his close personal ties to the man he might have to run against. As governor and senator, the Warners had a cordial relationship. But it became a friendship in 2004 after the senator was condemned by his own party for publicly supporting then-Gov. Warner's tax increases. At a news conference in Richmond, John Warner said: "Politics be damned. Let's consider what's best for the men and women of this great state and their families and children."

Aides have said the two grew closer after that. Mark Warner has said publicly in the past that he would not run against the senator.

John Warner said this week that the former governor had not discussed a possible challenge with him. "I know that he'd be talking to me if he were going to do this," the senator said. "I have not heard from him."

Asked if a challenge from Mark Warner would cause him to forgo a reelection bid, the senator replied: "My dear fellow, I've got it in me."