U.S. Democratic presidential candidate Hillary Clinton tried to raise doubts about surging rival Barack Obama on Thursday but said in an emotional debate finale that "whatever happens, we're going to be fine."

Clinton, her political life on the line based on whether she can win big victories in Texas and Ohio on March 4, questioned Obama's readiness to become commander-in-chief, said he has a weak resume and criticized him for borrowing rhetoric for his uplifting campaign speeches.

But in a passionate concluding statement - perhaps her most emotional since she shed tears in New Hampshire in January - she made reference to her past political battles from her husband's time in the White House, without detailing them.

Clinton, a New York senator, said she had "lived through some crises and some challenging" moments in her life but that they had been "nothing compared to what goes on every single day in the lives of people across our country."

"Whatever happens, we're going to be fine," she said, looking at Obama seated beside her. "We have strong support from our families and our friends. I just hope that we'll be able to say the same thing about the American people and that's what this election should be about."

Obama appeared touched by her words and the two shook hands warmly in the middle of her statement.

TIGHT RACES IN TEXAS, OHIO

They went into the debate with different objectives.

Obama, an Illinois senator who would be the first black president, wanted to protect his dominant position after 10 straight wins in the state-by-state nomination process.

Clinton, who would be the first woman president, wanted to try to shake up the race for the Democratic nomination to face the Republican Party's choice in November's election.

Whether she was successful was an open question.

In her toughest line of the night, she drew scattered boos from some in the audience for ridiculing Obama for using rhetoric in his speeches that had already been used by a supporter, Massachusetts Gov. Deval Patrick.

"If your candidacy is going to be about words, then they should be your own words," she said. "And you know, lifting whole passages from someone else's speeches is not change you can believe in, it's change you can Xerox."

Obama said the fuss over the lines he used from Patrick was "silly season" politics.

Scolding Clinton, he said Democrats should not be "tearing each other down" but rather "lifting the country up."

New Washington Post-ABC News opinion polls showed the two hopefuls about even in Texas, with Clinton at 48 percent and Obama at 47 percent, but Clinton leading Obama in Ohio by 50 percent to 43 percent.

Obama has a growing lead in pledged delegates who will choose the Democratic candidate at the party's convention in August.

The latest count by MSNBC gives Obama 1,168 delegates to Clinton's 1,018. The Democratic nominee will likely face Sen. John McCain of Arizona, the Republican front-runner, in the election to succeed President George W. Bush.

ACCOMPLISHMENTS

Clinton also tried to raise questions about her rival's resume, pointing to a supporter's inability to list a single Obama accomplishment when pressed to do so on Tuesday in an MSNBC interview.

"So I know there are comparisons and contrasts to be drawn between us," she said.

Obama defended his record testily, saying Clinton was trying to suggest his supporters "were being duped" by him. He said he had helped push the toughest ethics reform legislation in the Senate since the Watergate scandal of the early 1970s.

"Senator Clinton has a fine record. So do I," he said.

As she has done often in recent days, Clinton questioned whether Obama was ready to take the reins of power at a time of global unrest.

Obama pointed to his opposition to the Iraq war, and Clinton's 2003 vote in favour of a Senate resolution that authorized the Iraq war, as an example of his judgment.

He said that on "the single most important foreign policy decision" of the decade, "I believe I showed the judgment of a commander in chief and I believe Senator Clinton was wrong in her judgment on that."

Cuba, now that ailing Fidel Castro has stepped down, featured prominently in the debate as the two candidates courted Hispanics who could play an influential role in the Texas vote.

Obama expressed a willingness to move quickly toward a meeting with Castro's replacement, in line with his previous commitment to hold direct talks with leaders of hostile countries if he is elected president.

Clinton was more cautious, saying Cuba should first make progress on long-standing U.S. complaints about the need to improve human rights and release political prisoners.

Castro is expected to be replaced in power by his brother, Raul Castro, 76.