WASHINGTON – An undecided lawmaker on the Senate committee considering John Bolton’s nomination to be America’s ambassador to the United Nations yesterday said he was not particularly swayed by committee Democrats who argued that Mr. Bolton was wrong for the position.

“I don’t think the opposition has made as strong a case as they should,” Senator Chafee, a moderate Republican from the blue state of Rhode Island, said in an interview after the morning session of the Senate Foreign Relations Committee.

Mr. Chafee is the only Republican who has not yet said whether he would endorse Mr. Bolton. If he votes with the committee’s Democrats, and all of the Democrats side against Mr. Bolton, then the vote on the panel would be tied at 8-8, blocking the nomination from going to the Senate floor.

Mr. Chafee has a history of parting with his GOP colleagues. He was so critical of President Bush’s decision to go to war in Iraq that he wrote in Mr. Bush’s father’s name for the 2004 presidential ballot.

Mr. Bolton, who as undersecretary of state for arms control and international security affairs was tagged by critics as hostile to Turtle Bay, said in his opening statement: “I look forward to working closely with this committee to forge a stronger relationship between the United States and the United Nations, which depends critically on American leadership.”

Mr. Bolton said Secretary-General Annan last week told him he looked forward to working with him. “Get yourself confirmed quickly,” Mr. Bolton testified that Mr. Annan told him. A spokesman for Mr. Annan confirmed that the conversation took place but would not disclose what the two men said.

In his first round of questions, Mr. Chafee told Mr. Bolton he had “said all the right things” in his opening statement, although in a later interview, Mr. Chafee said he was withholding judgment. The senator, who is up for reelection next year, added, “I wish this hadn’t been the nomination. When I heard this, I thought, here comes some tough hearings.”

Senator Kerry, a Democrat from Massachusetts who lost the 2004 presidential election, sent an e-mail urging his supporters to call Mr. Chafee’s office asking him to reject Mr. Bolton. His political organization has also taken out ads against Mr. Bolton on Web sites that cater to Rhode Islanders.

Mr. Kerry and other senators from his party yesterday zeroed in on an incident they said proved Mr. Bolton tried to intimidate a State Department intelligence analyst, Christian Westermann, in spring 2002 about the analyst’s objections to a speech Mr. Bolton gave to the Heritage Foundation warning of Cuba’s clandestine efforts to make biological weapons.

Over the weekend, committee staff interviewed seven people regarding the allegations, including Mr. Westermann, his two immediate bosses in the State Department’s bureau of intelligence and research, and CIA officials.

When pressed about the incident, Mr. Bolton said, “He just wasn’t straight with me.” In particular, Mr. Bolton said he lost confidence in the analyst because Mr. Westermann had recommended his alternative and less ominous language on Cuba’s germ program to the CIA without properly consulting him first. But he also said he felt he had nothing to hide. “Release all of it,” Mr. Bolton said, referring to the transcripts of interviews and classified records the committee staff pored through prior to yesterday’s hearing.

Democrats like ranking member Senator Biden, from Delaware, charged that Mr. Bolton may have been motivated because Mr. Westermann challenged his more alarmist forecast. At one point, Senator Boxer, a Democrat from California, asked Mr. Bolton if he wished to apologize to Mr. Westermann for calling him in private communications “a mid-level munchkin.”

Midway through the hearing, the committee’s chairman, Senator Lugar, a Republican from Indiana, said, “At some point we are trying to bring this to conclusion. There is a disagreement on how grave the offense may have been.”

In addition to the alleged intimidation of intelligence officials, some Democrats also tried to paint Mr. Bolton as a radical opponent of the United Nations, repeating quotes he made in 1994 to the World Federalist Society, an organization that today calls itself Citizens for Global Solutions. The group has run ads in Rhode Island showing Mr. Bolton speaking at a 1994 conference, where he said, “If the U.N. secretary building in New York lost 10 stories it would not make a bit of difference.”

Senator Boxer played three minutes of the speech that was featured in the Citizens for Global Solutions Web site and political ads. Mr. Bolton responded: “The comment about the 10 stories is a reflection that there is not a bureaucracy in the world that could not be leaner.” He added that he tailored the remarks to the audience. “This is a group that believes in world government, and I do not.”

The hearing yesterday was not without theatrics. As Senator Dodd, a Democrat from Connecticut, was preparing to question Mr. Bolton, three women from the anti-war group “Codepink” stood up and began shouting at the committee to reject Mr. Bolton. Allison Yorra, one of the women, unfurled a sign that read, “Bolton equals nuclear proliferation.” Capitol Hill police escorted the three protesters out of the hearing room to a gaggle of 20 cheering supporters.

Carl Ford, the former assistant secretary of state for intelligence and research, will testify before the committee today.

The committee is expected to vote Thursday on Mr. Bolton’s nomination.