Updated

President Bush pressed hard Thursday to undermine Democrat John Kerry (search) as a prospective commander in chief, accusing the Massachusetts senator of waffling on Iraq and sending dangerously misleading signals to friend and foe alike.

Kerry, addressing National Guard veterans in Las Vegas, said Bush was the one "living in a fantasy world of spin" and failing to tell the truth on Iraq.

"Mixed signals are the wrong signals to send to our troops in the field, our allies and, most of all, our enemies," Bush said at a rally at a minor league baseball field in St. Cloud as he campaigned through southeastern Minnesota by bus.

Bush also kept up his criticism of Kerry's health care proposals, saying his rival's plans would create a multi-billion-dollar government enterprise that would restrict people's choices and drive private companies out of business.

The president campaigned in a state that Democrat Al Gore carried in 2000 and where Kerry is ahead in recent polls — but one that GOP strategists consider highly competitive.

Nationally, Bush has seemed to open a lead in the days following the Republican convention. However, a new national poll suggested the presidential contest had returned to a virtual dead heat.

While Kerry addressed the same National Guard (search) convention in Las Vegas that Bush had spoken to two days earlier, the president in Minnesota hammered at a favorite theme: that Kerry has continually changed positions on the war in Iraq.

"The fellow I'm running against has had about eight positions on Iraq," Bush said. "Yesterday, in a radio interview, he tried to clear things up," Bush said.

That was a reference to Kerry's interview the day before with talk show host Don Imus in which Kerry said that he could not envision invading Iraq "under the current circumstances" but also said it was right to hold Saddam Hussein accountable and that he had made the right decision in voting in 2002 to give Bush war authority.

Under indecisive leadership, Bush said, "the world will drift toward tragedy. This isn't going to happen on my watch." The crowd chanted, "Four more years."

Kerry said the problem was Bush's approach and failure to own up to the seriousness of the situation in Iraq.

"You deserve a president who will not play politics with national security, who will not ignore his own intelligence while living in a fantasy world of spin, and who will give the American people the truth about the challenge our brave men and women face on the front lines," the Democratic senator said in remarks prepared for the National Guard Association of the United States.

"Two days ago, the president stood right where I'm standing and did not even acknowledge that more than 1,000 men and women have lost their lives in Iraq. He did not tell you that with each passing day we're seeing more chaos, more violence, more indiscriminate killings," Kerry said.

With less than seven weeks before Election Day, the Democrats rolled out a new ad campaign.

It questions Bush's credibility in an ad showing him declaring an end to major combat in May 2003 while standing in a flight suit on an aircraft carrier adorned with a "Mission Accomplished" banner. "How can you solve problems when you won't even admit they're there?" asks the ad, which will start Friday in battleground states and on national cable networks.

The race may be tightening. A new poll from the Pew Research Center said the "bounce" that seemed to propel Bush to a lead just after the Republican convention had disappeared.

In polling from Sept. 8-10, Bush was ahead by 52-40 percent among registered voters and 54-39 percent among likely voters. But in follow-up polling from Sept. 11-14, the center found the race 46-46 among registered voters and 47-46 Bush among likely voters.

Iraq wasn't the only issue the candidates were focused on.

Bush's latest ad running in Michigan, Ohio and other battlegrounds says Kerry's health care plan would be controlled by the government. "Not true," Kerry's campaign said in an ad released Thursday.

Yes it was, Bush said in Minnesota, trying to counter an issue that polls show is one of his weakest. Kerry's plan, he said, "will crowd out private health insurance."

Bush's criticism followed accusations by Kerry at heath-care forums that the administration was manipulating reports to "hide the truth" that Medicare premiums will consume nearly 40 percent of the average older person's Social Security income by 2006.

Bush, trying to put Kerry on the run in a traditionally Democratic state, has started to spend more on advertising in Minnesota. That has forced Kerry to move up plans to advertise here. Bush's trip was his fifth to Minnesota this year. Kerry has made six stops.

In Blaine, just north of Minneapolis, the president addressed the controversy over buying cheaper drugs from Canada, telling his border-state audience, "I know it sounds attractive to some of you ... and it may work." He said his administration was studying the issue but was concerned that unsafe or ineffective drugs could find their way to Americans.

On his way from St. Cloud to Blaine, Bush stopped his bus caravan in the town of Anoka, where he grabbed a carryout lunch in the Brick House Deli.

"I'd like an egg salad sandwich. Fire one up," Bush said. His server, Tara Morrissey, said they didn't have egg salad — but had chicken salad. Bush said that was fine.