President Bush (search) and Sen. John Kerry (search), their animosity stirred by a contentious second debate, lit into each other over Iraq, jobs and debate performance on Saturday in critical battleground states.

Instant polls did not give either Bush or Kerry a clear edge in Friday's wide-ranging debate in St. Louis before an audience of uncommitted voters. But Republicans were heartened by what they saw as a steadier, more focused and aggressive performance by the president than in the first debate, where he displayed bouts of impatience and peevishness.

Kerry also criticized the administration for the shortage of flu vaccine.

"We now know the administration knew ahead of time that there wasn't going to be enough vaccine," Kerry asserted as he campaigned in Ohio. The administration has denied it had any warning.

Bush and Kerry ventured into each other's "must win" states. Bush campaigned in Iowa and Minnesota, states won by Democrat Al Gore (search) in 2000. Kerry had stops in Ohio and Florida, states won by Bush in 2000.

Campaigning in northeastern Ohio, Kerry accused the administration of misleading Americans on the flu vaccine shortage.

"The administration, we've learned today, is playing fast and loose again with the facts and the truth to the American people because they pretended and they've acted surprised that we didn't have the vaccines," Kerry said at a nursing school. "Rather than tell the truth to the American people, they've acted surprised and pretended it just sort of happened on their watch."

Kerry did not elaborate, but a story from London in Saturday's editions of the Washington Post quoted British health officials as saying their American counterparts were told in mid-September that problems at a drug manufacturing plant in northwest England could disrupt vaccine supplies to the United States.

A Food and Drug Administration statement disputed the British account, saying "there had been no communication" between the U.S. and British governments on the matter until the British government acted earlier this week.

Bush campaign spokesman Steve Schmidt called Kerry's criticism "baseless and hypocritical. So few companies make flu vaccines because of a broken medical liability system that Kerry falsely claims to want to fix but has voted 10 times against reforming."

Both candidates sharply critiqued the other's debate performance of the night before.

"The reason I thought he was making all those scowling faces was because he saw the latest job numbers," Kerry told about 10,000 people at a rally in this northeastern Ohio community. At another point, Kerry joked that he was "a little worried ... I thought the president was going to attack (moderator) Charlie Gibson."

Kerry said the nation's choice "could really not have been more clear than it was last night."

The Democrats' advisers said he plans intense attacks in the coming days over domestic issues, including job losses, rising health care costs, and stem-cell research, in the run-up to Wednesday's concluding debate in Tempe, Ariz.

Bush, speaking to more than 7,000 supporters at a Waterloo, Iowa, baseball field, declared himself the winner of the debate and ridiculed Kerry.

"With a straight face, he said, 'I had only one position on Iraq.' I could barely contain myself. He must think we've been on another planet," Bush said, and contended his opponent "doesn't pass the credibility test."

Bush repeated his attack on Kerry's credibility later at a rally in suburban Minneapolis, with his audience chanting "He can run, but he cannot hide" along with him.

Both sides worked to maximize weekend exposure in hopes of winning the post-debate "spin" battle to portray their respective candidate as emerging as the victor.

Bush used his weekly presidential radio address for a partisan attack on Kerry, declaring that his rival's proposals would "weaken America and make the world more dangerous."

Bush senior adviser Karl Rove, in a rare on-the-record talk with reporters traveling with Bush, defended Bush's more combative tactics in the second debate. "He was eager. He saw the opportunity to set the record straight. He had lots of fun," Rove said.

Rove continued to characterize the race as close, although he noted Bush was making headway in several states that had gone for Gore in 2000.

Democrats planned a busy weekend as well. Vice presidential candidate John Edwards (news - web sites) planned back-to-back appearances on all five television network Sunday interview shows.

Kerry adviser Joe Lockhart said Kerry will put particular emphasis on domestic issues in the final weeks of the campaign. "I think John Kerry scored very well any time the subject turned to jobs, the economy, health care and the environment," Lockhart told reporters in a conference call.

Edwards, campaigning in Detroit, accused the president of distorting the latest employment statistics during the debate to make it seem like millions of jobs had been created on his watch. "They're going to try everything they know how to put lipstick on this pig, but at the end of the day, it's still a pig," Edwards said.

Although 1.8 million jobs have been added to business payrolls in the past year, there are 821,000 fewer jobs now in the country than when Bush took office in January 2001.

Vice President Dick Cheney, campaigning in Florida, stressed the importance on building on the Republicans' slim Senate majority. "In a Senate as closely divided as it is today, every seat counts," he said at a fund-raiser for Republican Senate candidate Mel Martinez. The Senate has 51 Republicans, 48 Democrats and one Democratic-leaning independent.