WASHINGTON – A new campaign here to scuttle President Bush’s nominee for ambassador to the United Nations, John Bolton, is gathering steam. However, a swing voter on the Senate Foreign Relations Committee, Senator Hagel of Nebraska, yesterday announced that he would vote to confirm Mr. Bolton, which could prove a setback to those opposing the appointment.

Yesterday afternoon, Mr. Hagel, a Republican, said in a statement to the press, “I intend to support John Bolton’s nomination to be Ambassador to the United Nations. His experience and knowledge will serve him well as he represents America’s interests in the U.N. at a critical time. Mr. Bolton’s commitment to consult with members of Congress on a regular basis will be essential in helping him strengthen the U.N. and moving it toward reform.”

The endorsement by Mr. Hagel, who last year voted with Democrats on the Senate Select Committee on Intelligence to expand the Iraqi war inquiry to include the activities of the Pentagon’s office of special plans, is a blow to a new coalition of conservatives and progressives intent on derailing the Bolton nomination, which was announced last week.

Since then, moveon.org has asked its supporters to pressure members of the Senate Foreign Relations Committee to vote against Mr. Bolton. A letter to MoveOn members sent by one of its directors, Eli Pariser, compared the nomination to the selection of a felon to be a police chief. Another organization called Citizens for Global Solutions created a Web site devoted to striking down Mr. Bolton’s nomination. The site features video footage of remarks in which Mr. Bolton opined that if the U.N. Secretariat building in New York “lost 10 stories, it wouldn’t make a bit of difference.”

But Mr. Bolton’s detractors are not limited to liberal democrats. The executive vice president of the New America Foundation, Steve Clemons, who has worked in recent months to bring Republican critics of the Iraq war together with Democrats, has utilized his blog in the last week to organize grass roots opposition to Mr. Bolton’s nomination.

On his web log, www.thewashingtonnote.com, Mr. Clemons boasted that phone calls to the Senate Foreign Relations Committee from his readers last week forced the panel to postpone Mr. Bolton’s confirmation hearings until after the Easter recess. A spokesman for the committee, Andy Fisher, however, disagreed with that account. “Their campaign has no relevance whatsoever on when we decided to hold the hearing,” he said. “Senator Lugar tries to bring up the hearings as soon as possible. In this case he would like to have the hearing on April 7. It would have been impossible to have it before then.”

Mr. Clemons said that his sources in the State Department and on the committee said that there was a push to hold the hearings sooner, making it difficult to muster momentum against the nomination.

Mr. Clemons said the nomination of Mr. Bolton would be blocked if all of the Democrats on the Senate Foreign Relations Committee opposed it and one Republican broke ranks. With Mr. Hagel’s endorsement of Mr. Bolton, that leaves Senator Chafee. “I think this goes out of committee the battle becomes harder for opponents of Bolton,” Mr. Clemons said. “If we are able to keep [Democratic Wisconsin Senator] Feingold from supporting Bolton and turn Chafee then we will win.”

Mr. Bolton has been busy in recent days with meetings and phone calls with members of the Senate Foreign Relations Committee. He has met with Mr. Hagel as well as Senator Chafee, a moderate Republican from Rhode Is land, who has clashed with the White House on the Iraq war as well as social security reform.

Mr. Chafee, who last fall cast his ballot in protest for George H.W. Bush and not his son, issued a statement that appeared designed to keep his options open on the matter. “The nomination of Undersecretary of State John Bolton brings a seasoned member to the Diplomatic team that will represent us through some very difficult times ahead,” his statement said. “Undersecretary Bolton has been an outspoken critic of the United Nations. However, I have been assured that he will bring a more balanced approach to his new role.” The second-to-last line of the statement, though, left open the possibility Mr. Bolton’s name could not get out of committee: “I look forward to speaking with Undersecretary Bolton at his confirmation hearings about the myriad issues that he will be confronting if he is confirmed.” A spokesman for Senator Feingold told the Sun yesterday that he was reserving judgment about Mr. Bolton’s nomination until the hearings scheduled for April 7.

Supporters of Mr. Bolton yesterday were confident their man would be confirmed by the Senate. “If the committee gives John Bolton a fair hearing, which I expect they will, John will prove to be a very formidable and articulate defender of his positions,” the executive director of the Project for a New American Century, Gary Schmitt said. “At the end of the day the president will get his man, precisely because John represents what the president wants when it comes to reforming the United Nations.”