On the Republican side, likely nominee John McCain said that if he could not persuade Americans that U.S. policy in Iraq was succeeding, "then I lose. I lose." Speaking to reporters during a campaign visit to Ohio, the Arizona senator quickly sought to backtrack and said, "I'd like to retract 'I'll lose,' " though he acknowledged he was closely tied to the U.S. military surge and to support for an ongoing American presence in Iraq.

The increasingly intense rhetoric between the Democratic contenders was a prelude to their debate tonight in Cleveland, the last before primaries next Tuesday in Ohio and Texas that could determine the fate of Clinton's candidacy. She has said she plans to make her experience a focus of the remainder of the primary campaign.

Speaking yesterday at George Washington University, Clinton chided Obama for what she said was a lack of experience that could rival a Bush administration that had a strategy based on a series of "false choices and then is indifferent about the consequences - force vs. diplomacy, unilateralism vs. multilateralism, hard power vs. soft."

"We've seen the tragic result of having a president who had neither the experience nor wisdom to manage our foreign policy and safeguard our national security," she said. "We can't let that happen again."

Clinton cited her background of having been in the White House with her husband during crises, as well as her service as a two-term New York senator on the Armed Services Committee.

Her remarks were the latest example of trying to leverage President Bush's unpopularity among Democrats and independents onto Obama. She previously had accused Obama's campaign of using Republicanlike tactics to criticize her on health care and trade.

At campaign rallies in Cincinnati and Dayton, Ohio, Obama did not directly address Clinton's speech. Instead, he left the task to surrogates who also sought to echo his anti-NAFTA message against Clinton.

Susan Rice, an assistant secretary of state in Bill Clinton's administration who is now an Obama foreign-policy adviser, said even before the speech that Sen. Clinton's foreign-policy record showed poor judgment, foremost in her vote to authorize the war in Iraq.

Rice also cited Sen. Clinton's support for a Senate resolution urging the Bush administration to declare Iran's Revolutionary Guard a terrorist organization - a measure that the Obama camp has argued would provide political cover for people in the administration who are urging a military attack on Iran.

Borrowing a theme repeated frequently by Obama, Rice said: "What is important on Day One is to get it right and have the right judgment."

With Ohio's manufacturing industry devastated by job losses to foreign competitors and the North American Free Trade Agreement deeply unpopular in the state, Obama's campaign also enlisted labor leaders to attack the role of Bill Clinton's administration in winning passage of the accord.

Obama has argued that Hillary Clinton's campaign is trying to take credit for the favorable parts of her husband's administration while distancing itself from negative aspects.

"The Clinton administration was not only the architect of NAFTA but shoved it down the throats of Democrats in Congress," said Bruce Raynor, general president of UNITE HERE, a union representing industrial and textile workers and hotel and restaurant employees.

Responding to Obama's repeated criticism on NAFTA, the Clinton campaign began its own effort to reach out to voters. "NAFTA has hurt Ohio families and I have a plan to fix it," she says in an automated telephone call to voters.

McCain, meanwhile, surprised reporters by saying he would lose if he failed to persuade voters troubled by the situation in Iraq that the war effort was worth it.

After asking to retract his statement, he said voters "first and foremost" would decide whether he could lead the country. "Obviously, Iraq will play a role in their judgment of my ability to handle national security," he said.