JACKSON, Miss. - Calling Sen. Trent Lott too politically weakened to do his job, Republican Sen. Don Nickles of Oklahoma called yesterday for new elections to replace Lott as Senate majority leader, a major blow for the embattled Mississippi Republican.

Nickles, the assistant Senate Republican leader who has long coveted the top leadership spot, broke with party members who have tried to publicly shore up support for Lott. By day's end, Sen. Chuck Hagel of Nebraska also said GOP senators should address the dispute to determine whether Lott is fit to be the party's leader in the Senate.

Lott has been struggling since Dec. 5 to quell an outcry that erupted after he suggested that the nation would have been better off if Republican Sen. Strom Thurmond of South Carolina had been elected president in 1948 when he ran on a pro-segregationist platform for the States' Rights Democratic Party.

Lott made the remarks at a 100th birthday party for Thurmond in Washington. At first he dismissed his words as "lighthearted" when asked what he meant. Later, when the furor intensified, Lott apologized several times, calling segregation "a stain on our nation's soul."

But Nickles, who had remained conspicuously silent during the past week, indicated that the apologies might not solve the problem Lott created for the Republican Party.

"I am concerned that Senator Lott has been weakened to the point that may jeopardize his ability to enact our agenda and speak to all Americans," Nickles said in a statement. "There are several outstanding senators who are more than capable of effective leadership, and I hope we have an opportunity to choose."

Later, in a taped interview with ABC's This Week, Nickles questioned how Lott could push President Bush's legislative agenda through the Senate and serve as the public face of Senate Republicans.

"Can he be effective? Can he campaign in places like Chicago?" Nickles asked. "I don't want to squander our ability to get things done. We only have a short window this year."

In a statement issued last night, Lott's office did not address Nickles' move directly but said only that Lott looks forward to appearing on Black Entertainment Television "to discuss the serious issues of diversity, opportunity and race in America," The New York Times reported.

In recent days, Nickles, who is losing his No. 2 leadership post because of term limits and will become Budget Committee chairman, has been calling his GOP colleagues, trying to get a sense of whether he would have support to challenge Lott.

Brook Simmons, a spokesman for Nickles, said the senator called top presidential adviser Karl Rove on Saturday night to notify the White House of his decision to release the statement about Lott. He said Nickles also called Lott yesterday.

"Senator Nickles felt that someone had to say it publicly because others have said it privately," Simmons said.

When asked if Nickles will run for Lott's job, he said, "We have not crossed that bridge yet. Nickles is not saying it has to be him, but it has to be another senator."

In a statement yesterday, Hagel said: "Republican senators must either reconfirm their confidence in Senator Trent Lott's leadership or select a new leader.

"The American people must have confidence in their congressional leadership. In the interest of the Republican Party, the president's agenda and the nation, this issue must be resolved quickly."

While Nickles was calling for new elections, several other Republicans were still trying to defend Lott. Sen. Rick Santorum of Pennsylvania spoke up for Lott on NBC's Meet the Press, and Sens. John W. Warner of Virginia and Richard C. Shelby of Alabama backed him on CNN's Late Edition.

Warner called Lott "a fine leader" but also said it is up to the 51 GOP senators to decide how to handle the situation.

"It is our responsibility as a group to come together, make a decision and then go forward, not to let this thing be dangling out there day after day," Warner said. "I don't think it's fair to the party."

Said Shelby: "I think we should not lynch him. I believe right now that Lott would have the confidence of the caucus."

Republicans had unanimously re-elected Lott as their leader when the dispute erupted. Although Lott has never been wildly popular with his GOP conference, no senator stepped forward to challenge him.

Senators have long complained that Lott is too quick to cut deals with Democrats and that he is not effective at communicating the Republican message to the nation.

Several other Republican senators have been mentioned in recent days as possible successors to Lott. They include Nickles; Santorum; Kentucky Sen. Mitch McConnell, who was elected assistant majority leader to replace Nickles; and Tennessee Sen. Bill Frist, who was chairman of the Senate GOP campaign committee.

Republican rules require five senators to request a meeting of the conference. Nickles has not asked his colleagues to call such a meeting. But many senators have expressed anxiety in recent days because the controversy has not died down.

If Republicans do decide to dump Lott and hold new elections, friends have indicated that he might leave the Senate rather than stay in office without a leadership position. In that case, Mississippi Gov. Ronnie Musgrove, a Democrat, would appoint Lott's replacement. That could move the Senate back to its 50-50 status, though Republicans would retain nominal control because the vice president votes to break ties in the chamber.

Some Republicans have worried that if the Senate is evenly divided, Sen. Lincoln D. Chafee of Rhode Island might leave the party and become an independent or Democrat, throwing control back to the Democrats as happened last year with Sen. James M. Jeffords of Vermont.

Chafee has said he is worried that if Lott is thrown out as majority leader, his replacement will be more conservative.

Jill Zuckman is a reporter for the Chicago Tribune.