But the U.S. Senate vote due to take place today is expected to confirm him to a post that has been vacant since January. Republicans hold a 55-44 edge in the Senate, and most have said they will respect President George W. Bush's wish to have Bolton lead reform efforts at the United Nations.
Republican Senator Richard Lugar (Indiana), who chairs the Foreign Relations Committee, said yesterday that it has been the most intense examination of a nominee in his experience. But he said many of the charges raised by Democrats against Bolton -- such as manipulating intelligence -- were not supported by the facts.
Addressing the full Senate, Lugar cited Bolton's achievements during the past four years as the Bush administration's undersecretary of state for disarmament. He pointed to the multinational proliferation security initiative, a deal to end Libya's weapons of mass destruction program, and an effort by rich nations to fund nonproliferation efforts, mainly in Russia.
"Opponents have argued that Secretary Bolton's personality will prevent him from being effective at the UN," Lugar said. "But his diplomatic successes over the last four years belie that expectation."
Democratic senators said they would seek to avoid a vote on the nomination until they receive more documents from the Bush administration that could provide details about whether Bolton tried to influence intelligence assessments.
The Democrats received one of their strongest boosts from a Republican senator -- George Voinovich of Ohio. Voinovich nearly blocked the nomination in the Senate's Foreign Relations Committee and sent a note this week to all senators urging them to vote against Bolton.
Voinovich portrays Bolton as an aggressive partisan who would undermine U.S. efforts to build support for key initiatives at the United Nations. The senator urged his colleagues to consider their vote carefully.
"We're going to vote tomorrow. And I'm afraid that when we go to the well (hold the vote), that...too many of my colleagues are not going to understand that this appointment is very, very important to our country," Voinovich said. "At a strategic time when we need friends all over the world, we need somebody up there who's going to be able to get the job done."
Several other Republicans have expressed doubts about Bolton. But they say they expect him to fulfill his pledge to carry out the administration's stated policy to strengthen the United Nations.
Senator Christopher Dodd (Democrat, Connecticut) said his party does not plan to block the nomination through procedural moves. But he said the Senate should assert its right to seek information from the administration on a nominee.
"If the administration -- this administration or any administration -- believes that they can successfully deprive legitimate requests for information pertaining to a matter that's before us, particularly one that evokes as much debate as this nomination has, then we all suffer," Dodd said.
Republicans and Democrats in the Senate generally agree on the need for broad reforms at the United Nations, citing the tainted oil-for-food program in Iraq as a case in point. But their debate has revealed fundamental disagreements over the type of individual who can lead change at the United Nations.