LAS VEGAS, Nev. — Under pressure in a feisty debate, Sen. Hillary Rodham Clinton accused her closest rivals Thursday night of slinging mud "right out of the Republican playbook" and leveled her sharpest criticism of the campaign at their records.

"People are not attacking me because I'm a woman; they're attacking me because I'm ahead," Clinton said, striving to protect her standing as front-runner in an increasingly competitive nominating campaign.

"What the American people are looking for right now is straight answers to tough questions, and that is not what we have seen from Senator Clinton on a host of issues," said Sen. Barack Obama of Illinois in the opening moments of a debate seven weeks before the first contest of the race for the Democratic presidential nomination.

"There's nothing personal about this," said former Sen. John Edwards of North Carolina, who joined Obama in bluntly accusing Clinton of forever switching positions on Social Security, driver's licenses for illegal immigrants and other issues, turning aside the suggestion she was seeking to hide her positions. Long an advocate of universal health care, she said Obama's current proposal leaves millions uncovered and Edwards did not support health care for all when he first ran for president in 2004.

The three-way confrontation at the beginning of a lengthy debate reduced the other Democratic presidential hopefuls on the debate stage to the uncomfortable role of spectator, yet it perfectly captured the race for the party's nomination. Clinton leads in the nationwide polls, but recent surveys in Iowa show she is in a virtual dead heat with Obama and Edwards.

For New Mexico Gov. Bill Richardson, Sens. Joseph Biden of Delaware and Chris Dodd of Connecticut and Rep. Dennis Kucinich of Ohio, the opening moments were frustrating — and they repeatedly tried to break in. "Oh, no, don't make me speak," Biden said in mock horror when moderator Wolf Blitzer of CNN called on him roughly 15 minutes into the proceedings.

Richardson, who has campaigned in Nevada more than any other presidential hopeful, took verbal shots at Clinton and her two closest pursuers in the polls. "Let's stop the mudslinging," he said.

He said Edwards is engaging in class warfare, Obama was trying to start a generational war and Clinton "with all due respect with her plan on Iraq doesn't end the war. All I want to do is give peace a chance."

Richardson was in the minority when the candidates were asked whether human rights could ever trump national security.

He said it could; Clinton said it could not, and Dodd said "obviously national security." Obama challenged the question, saying "the concepts are not contradictory."

Clinton seemed intent on redeeming what even she conceded was a subpar performance at the previous debate, turning aside criticism from her rivals and answering questions with practiced ease.

Asked whether she was guilty of playing the "gender card" in her drive to become the first female president, she said she had not. "I'm not playing the gender card here in Las Vegas," a magnet for gamblers. "I'm trying to play the winning card," she said.

Obama was the first to challenge Clinton, saying it took two weeks to "get a clear answer" on whether she supports or opposes issuing driver's licenses for illegal immigrants. "The same is true on Social Security," he said.

For the first time in a debate since the campaign began, Clinton swiftly answered in kind. "When it came time to step up and decide whether or not he would support universal health care coverage, he chose not to do that," she said of Obama. She added his plan would leave 15 million people without coverage — the population of Iowa and three other early voting states in the nominating campaign.

Edwards was next to accuse Clinton of trying to have it both ways — with the war in Iraq, Social Security and defining the scope of President Bush's power to use military force against Iran. "She says she will bring change to Washington while she continues to defend a system that does not work, that is broken, that is rigged, that is corrupt," added the former North Carolina senator.

"I've just been personally attacked again," Clinton broke in. "I don't mind taking hits on my record on issues, but when somebody starts throwing mud, at least we can hope it's accurate and not right out of the Republican playbook."

The debate unfolded on a stage at the University of Nevada-Las Vegas. The state holds caucuses Jan. 19 — following Iowa on Jan. 3 and most likely the New Hampshire primary several days later.

The focus on Clinton from the debate's opening moments was hardly surprising.

The New York senator has conceded she turned in a less-than-sensational performance at the last debate, when she stumbled on a question about driver's licenses for illegal immigrants. Her husband, the former president, leapt to her defense in the interim, saying of her rivals: "Those boys have been getting tough on her lately."

The setting underscored Nevada's newly prominent role in the nominating process. The state is far more racially diverse than either Iowa or New Hampshire, with a population that is about 22 percent Hispanic and 10 percent black.

Democrats in Nevada hoped the focus on their state would prompt candidates to pay closer heed to Western issues like water, grazing and mining rights. But it was more than an hour into the two-hour debate before the issue of energy came up.

Instead, Clinton drew the first question — and moments later the first barb from Obama.

Despite her critics, she said, "I think the American people know where I've stood for 35 years," adding she had been fighting for children, workers, families and universal health care.

More than an hour later, Dodd sought to turn the focus back onto Clinton, saying she had changed positions on trade by announcing her support for a deal with Peru at the same time she advocates a "time out" for such agreements.

Moments earlier, Clinton gave a careful answer when asked whether she now viewed the North American Free Trade Agreement — a product of her husband's administration — to be a mistake.

"NAFTA is a mistake to the extent it did not deliver what we hoped it would," she said.

And she fielded another question about NAFTA with a quip. Asked whether she now believes Ross Perot when he argued against NAFTA in a 1993 debate with her husband's vice president, Al Gore, she said: "All I can remember from that is a bunch of charts," a reference to Perot's penchant for presenting information in made-for-television format.