President Bush and Democratic challenger John F. Kerry tangled again over Iraq in a series of pointed exchanges Friday night, with the president charging that Kerry would have left Iraqi President Saddam Hussein in power and made the world more dangerous. Kerry responded that it was Bush's war policies that have left the world less safe.

In a 90-minute town-hall-style debate, the two sharply disagreed on a wide range of issues, from national security to the economy, from taxes, deficits and health care to the ethics and morality of stem cell research. They outlined contrasting governing philosophies and the stark choices for voters in an election that remains deadlocked and increasingly contentious.

The debate repeatedly turned personal, reflecting the heated rhetoric the two have used on the campaign trail over the past week, with Bush accusing Kerry of a record studded with inconsistency and liberal values. "I can see why people think that he changes position quite often, because he does," Bush said.

The senator from Massachusetts responded that Bush's campaign has become a "weapon of mass deception" designed to dupe voters and hide a record of failure at home and abroad. "The president's just trying to scare everybody here," Kerry said.

After his performance of a week ago, in which he was caught scowling and frowning during Kerry's responses, Bush kept his facial expressions largely in check, even trying to make a joke at one point. In responding to a comment from Kerry, he quipped, "That answer almost made me want to scowl." Both found themselves on the defensive at times -- Bush on Iraq and the deficit, and Kerry on stem cell research and his Senate record.

But humor took a back seat throughout the night as the candidates fielded questions from an audience of citizens selected because they were uncommitted in the presidential race or softly aligned to either Bush or Kerry. The questioners took Bush and Kerry through a thicket of issues, prodding and probing and challenging each on his record and his promises for the future. The debate was held on the campus of Washington University, with ABC-TV's Charles Gibson serving as moderator.

The most intense disagreements came again over Iraq, an issue where Bush has been on the defensive this week. A report by the chief U.S. weapons inspector, Charles A. Duelfer, concluded that Hussein had eliminated his illicit weapons after the 1991 Persian Gulf War and did not have either stockpiles of banned weapons or the capacity to produce them when the United States invaded Iraq in March 2003.

Bush vigorously defended the decision to go to war. "I tried diplomacy," he said, "went to the United Nations. But as we learned in the same [Duelfer] report I quoted, Saddam Hussein was gaming the oil-for-food program to get rid of sanctions. He was trying to get rid of sanctions for a reason: He wanted to restart his weapons programs."

Bush said that "we all thought there was weapons there," including Kerry, but that Hussein was a unique threat and the world is better off with him removed from power. "And my opponent's plans lead me to conclude that Saddam Hussein would still be in power," he said, "and the world would be more dangerous."

Kerry said Bush rushed to war without winning the support of more allies and did not listen to some military leaders who argued for more troops in Iraq. "The world is more dangerous today because the president didn't make the right judgments," Kerry charged.

Kerry argued that Bush had broken a pledge made four years ago in a debate, saying Bush then had promised not to go to war without an exit strategy or enough forces to get the job done. "He didn't do that. He broke that promise," Kerry said.

If Bush had let U.N. inspectors continue their work, Kerry said, Hussein could have been contained and "we wouldn't have 10 times the number of forces in Iraq that we have in Afghanistan chasing Osama bin Laden." In the meantime, Kerry charged, Bush has ignored growing dangers posed by the nuclear programs of Iran and North Korea.

Bush said he is keeping his eye on those problems, reminding the audience that he had dubbed those countries, along with Iraq, as an "axis of evil." He charged that Kerry's call for bilateral negotiations with North Korea would undercut six-party talks already underway and said the United States was working with Britain, France and Germany to deliver a stern message to Iran about its nuclear ambitions.

On Iraq, Bush said Kerry's apparent faith in international institutions and sanctions was misplaced, given Hussein's history, and said Kerry seems to have changed his view of whether Hussein was a genuine threat. "He keeps talking about 'Let the inspectors do their job.' It's naive and dangerous to say that. That's what the Duelfer report showed. He [Hussein] was deceiving the inspectors."

Both candidates tried to dispel talk that the United States might need to reinstate the military draft because of overextended forces. "Forget all this talk about a draft," Bush said. "We're not going to have a draft so long as I am the president."

Kerry said he, too, opposes a draft but said he would be a better commander in chief by emulating former presidents Ronald Reagan and Dwight D. Eisenhower and working more cooperatively with allies. "We're not going to go alone like this president did," he said.

Bush shot back: "Tell [British Prime Minister] Tony Blair we're going alone. Tell [Italian Prime Minister] Silvio Berlusconi we're going alone. Tell Aleksander Kwasniewski of Poland we're going alone. There are 30 countries there. It denigrates an alliance to say we're going alone, to discount their sacrifices. You cannot lead an alliance if you say . . . you're going alone."

To a question about America's frayed alliances, Bush said he recognizes that many of his decisions have been unpopular but argued they are good for the country. "I don't think you want a president who tries to become popular and does the wrong thing," he said.

The debate took place on a day when the Labor Department issued a monthly employment report showing the economy had produced 96,000 jobs last month, well below forecasts, with the unemployment rate unchanged at 5.4 percent. That left Bush in the position of being the first president since Herbert Hoover not to have produced job gains during his first term in office.

"The president has presided over an economy where we've lost 1.6 million jobs. The first president in 72 years to lose jobs," Kerry said in response to a question about allegations that he has flip-flopped. "I have a plan to put people back to work. That's not wishy-washy."

Overall, Bush said little about jobs through the night, noting that 1.9 million new jobs have been created in the past 13 months but omitting that the nation has still seen a net loss in payroll slots since he took office. Bush, speaking of what he called Kerry's liberal voting record, referred to him as "Senator Kennedy" and did not correct himself.

Kerry hammered Bush several times on the return of the federal budget deficit, which had been eliminated under President Bill Clinton. Kerry charged that Bush has "added more debt to the debt of the United States in four years than all the way from George Washington to Ronald Reagan put together -- go figure."

Bush defended his stewardship of the budget, pointing to the recent recession and the cost of war. The president said he is "concerned about the deficit, but I am not going to shortchange our troops in harm's way." He added: "And I'm not going to run up taxes, which will cost this economy jobs."

Kerry has said he would roll back Bush's tax cuts only on people making more than $200,000 a year, and one audience member pushed him to take a pledge, asking whether Kerry would be "willing to look directly into the camera and, using simple and unequivocal language," pledge not to raise the tax burden on families making less than $200,000 a year.

"Absolutely," Kerry replied. "Yes. Right into the camera. Yes. I am not going to raise taxes. I have a tax cut."

One of the more personal exchanges between the candidates resulted from a questioner's challenge to Kerry's call for the expansion of federally funded embryonic stem cell research, asking, "Wouldn't it be wise to use stem cells obtained without the destruction of an embryo?" Kerry, clearly uncomfortable with the question, said he respects the morality behind it but said he thinks "it is respecting life" to reach for cures in an ethical way. "The president has chosen a policy that makes it impossible for our scientists to do that," he said. "I want the future, and I think we have to grab it."

Bush, who decided in 2001 to permit limited federal funding for research on existing embryonic stem cell lines, said the nation has to be "very careful in balancing the ethics and the science." "To destroy life to save life is -- it's one of the real ethical dilemmas that we face," he said.

Kerry then accused Bush of "walking a waffle line," adding: "He says he's allowed it, which means he's going to allow the destruction of life up to a certain amount and then he isn't going to allow it."

Abortion produced another sharp exchange. Asked how he would respond to a "voter who believed abortion is murder and the voter asked for reassurance that his or her tax dollars would not go to support abortion," Kerry talked about the importance of his faith as a Roman Catholic but said, "I can't take what is an article of faith for me and legislate it for someone who doesn't share that article of faith."

"I'm trying to decipher that," Bush responded. "My answer is, we're not going to spend taxpayers' money on abortion."

Near the end of the debate, Bush was asked to cite three mistakes and what he did to correct them. He replied he made some hiring mistakes and that on the war there are "a lot of tactical decisions that historians will look back and say, he shouldn't have done that." But on the big question of going to war in Afghanistan and removing Hussein by force, he said, "I'll stand by those decisions because I think they were right."

Kerry said Bush had made a "colossal mistake" and asked voters to make a "gut check" on the dominant issue of the campaign: "Was this really going to war as a last resort?"

Researchers Lucy Shackelford and Alice Crites in Washington contributed to this report.

President Bush answers a question while Democratic challenger John F. Kerry listens during their second campaign debate, in St. Louis.President Bush and Sen. John F. Kerry participate in a town-hall-style debate at Washington University in St. Louis.