TOLEDO, Ohio - A debate over what might have happened to hundreds of tons of explosives gone missing in Iraq is leading President Bush and Sen. John Kerry to raise overarching questions about who responds best under the pressure of war and the threat of terrorism.

The candidates, carrying their argument into tours of battleground states in the closing days of the presidential campaign, are also framing policies concerning Iraq in terms of support for the men and women fighting there. Bush accuses Kerry of "denigrating" them; Kerry insists "you don't honor American troops by putting them in greater danger than they ought to be."

Bush contended that his Democratic opponent is making "wild charges" about explosives once stored at an Iraqi depot center and said an investigation is under way to determine what happened to them. Kerry and his running mate, John Edwards, questioned the administration's defense that the materials might have been removed before U.S. troops arrived.

"They had a responsibility to secure this material," Edwards said in an interview broadcast on NBC's "Today" this morning. "It was important for securing Iraq, it was important for the safety of our troops, it was important for keeping that material out of the hands of terrorists. And what we know is, they didn't do it."

One of Bush's supporters, former New York City Mayor Rudolph Guiliani, said the troops in Iraq bore the responsibility for searching for the explosives, not the president, and said no one knows if any mistakes were made.

"John Kerry wants to pretend we do know what happened," Guiliani told "Today." "We don't know what happened. The best possibility is that those explosives were gone even before the troops got there ... at least it's an equal possibility. John Kerry hasn't admitted that. Instead, John Kerry became an attack dog. He immediately began attacking the president."

Bush was stumping in Michigan, Ohio and Pennsylvania, in the reverse order of a Pennsylvania-Ohio-Michigan swing Wednesday that was capped by an early evening crowd of close to 20,000 at the Pontiac, Mich., Silverdome, one of the best turnouts of his campaign. Kerry was focusing on Ohio and Wisconsin before swinging south to spend Friday in Florida.

The Democrat kept up his drumbeat of criticism over the circumstances surrounding the disappearance of nearly 400 tons of explosives during the fall of Saddam Hussein's government.

"The missing explosives could very likely be in the hands of terrorists and insurgents, who are actually attacking our forces now 80 times a day on average," Kerry said in Iowa.

The president struck back by saying the senator simply does not know what happened there.

"A political candidate who jumps to conclusions without knowing the facts is not a person you want as your commander in chief," Bush told supporters Wednesday. "The senator is denigrating the action of our troops and commanders in the field without knowing the facts."

That brought a sharp rejoinder from Edwards as he campaigned in Kendall, Fla.: "Aren't we sick and tired of George Bush and Dick Cheney using our troops as shields to protect their own jobs?"

"Here's the truth, and the American people know it," Edwards said. "Our troops, our military did their job. George Bush is not doing his job."

The accusations flew in staccato phrases.

"Dodging and bobbing and weaving," Kerry said to describe his view of Bush's response to the missing explosives and all else that has gone wrong in Iraq.

"Wait and see and cut and run," Bush said to describe his view of the Democrat's likely brand of crisis management.

In a spirited rally in Cedar Rapids, Iowa, Kerry plugged his plans for health care, education and rural advancement. He said that as president he would hold a summit in Ames, Iowa, to firm up his farm proposals.

The Kerry campaign put the crowd to work, handing out phone numbers of voters to call on the spot. "I want you to reach out and convert someone on the other side," Kerry said.

Polls suggest Bush and Kerry are running even not only in Iowa and Michigan, but in an improbable variety of other battleground states and nationally as well. Bush, too, pressed hard for crossover votes.

"If you're a Democrat, and your dreams and goals are not found in the far left wing of the Democrat party, I'd be honored to have your vote," he said.

In Iraq, U.S. military maneuvers including stepped-up air strikes raised the prospect of a decisive showdown with insurgents in Fallujah and neighboring Ramadi. The goal would be to restore government control for the Iraqi national elections by the end of January.

Vice President Dick Cheney said Wednesday night in Wisconsin that the terrorists and insurgents "know once those elections are held, they're out of business. They've said as much" in "communications that we've captured between Zarqawi and the bin Laden crowd." Cheney was referring to terror mastermind Abu Musab al-Zarqawi.

Capping a political campaign already fixated on Iraq, any attack before Tuesday would send unpredictable reverberations through the U.S. electoral scene. Officials have not confirmed a major assault is close.

Bush's team put extra money into TV commercials in Portland, Maine, aimed at voters in neighboring New Hampshire, where the president is going Friday and polls find Kerry leading narrowly. The race in Hawaii, ordinarily a safe bet for a Democrat, was unexpectedly close.

Both sides are working feverishly to get out the vote. Many Americans, however, have already gotten out and voted.

An Associated Press-Ipsos survey found 11 percent of voters had already marked ballots in 32 states that permit early voting, and another 11 percent said they intended to do so before Tuesday.