President Bush taunted rival John F. Kerry here Tuesday over what he called another Kerry reversal on Iraq, seeking to put his challenger on the defensive over the central foreign policy issue of the election as he campaigned through heavily Republican territory in this battleground state.

On the opening day of a five-day campaign swing in which he was joined by Sen. John McCain (R-Ariz.), Bush seized on remarks Kerry made on Monday in which the Massachusetts senator defended his October 2002 vote to give Bush the authority to go to war in Iraq.

"Almost two years after he voted for the war in Iraq and almost 220 days after switching positions to declare himself the antiwar candidate, my opponent has found a new nuance," Bush said at a boisterous rally in Pensacola. "He now agrees it was the right decision to go into Iraq."

Bush added that "after months of questioning my motives and my credibility, Senator Kerry agrees with me that, even though we have not found the stockpile of weapons we all believe were there, knowing everything we know today, he would have voted to go into Iraq and remove Saddam Hussein from power." Then, with sarcasm in his voice, the president concluded: "I want to thank Senator Kerry for clearing that up."

As he campaigned by bus across the Florida Panhandle, Bush offered a hawkish defense of his decision to take the nation to war in Iraq, saying he had led with principle and conviction while portraying his opponent as someone torn by indecision, even naivete. Kerry, he said, exhibited a "dangerous misunderstanding of the enemy we face" in saying that Bush's policies in Iraq have created more terrorists. "We don't create terrorists by fighting back," Bush said. "We defeat terrorists by fighting back."

Campaigning Tuesday night in Las Vegas, Kerry criticized Bush for failing to build international support for the war and to plan for its aftermath.

"I thought the United States needed to stand up to Saddam Hussein, and I voted to stand up to Saddam Hussein," Kerry told a crowd of about 15,000 at the University of Nevada.

"I thought we ought do it right. We ought to reach out to other countries. We ought to build an international coalition. We ought to exhaust the opportunities available to us," Kerry said. "I will never send you into war without a plan to win the peace."

"Working with other countries, building support, is not a sign of weakness," the Massachusetts senator added. "It is a sign of strength."

As Bush and Kerry traded words over Iraq, the president got a strong vote of confidence from McCain, who had been courted by Kerry as a possible running mate and who only days ago defended Kerry's service in Vietnam after attacks from other Vietnam War veterans.

"The president took the fight to the enemy," McCain said as he introduced Bush in Pensacola. "This president went to Afghanistan and rid them of an evil regime that used to enjoy on Saturdays killing women in soccer stadiums. This president went to Iraq. It is a noble and just cause, and believe me, America, the world and Iraq is a better place for having been liberated."

Saying Bush has led with "great moral clarity and firm resolve," McCain added: "He knew that he and our country he leads has to commit to unconditional victory against our enemies. And that victory is to vanquish international terrorism -- not reduce it, not change its operations, not temporarily subduing it, but vanquish it. . . . He has not wavered. He has not flinched from the hard choices."

Bush's message was that Kerry has wavered repeatedly, as he again drew attention to the Democratic nominee's vote last year against the $87 billion spending authorization for Iraq and Afghanistan. "Senator Kerry tried to explain his vote this way: 'I actually did vote for the $87 billion before I voted against it,' " Bush said to laughter.

Bush drew a question here from a woman whose brother is heading to Iraq. She asked whether the administration has an exit strategy there. "All of us want the troops out," the president said, "but what we don't want is to cut short the mission. We don't want politics to decide the mission." The mission, he said, is "a free Iraq," adding that artificial deadlines for withdrawing U.S. forces would only encourage the insurgents while telling the Iraqi people "we're going to quit on you."

Bush began his bus tour in Pensacola, where McCain had been stationed as a young Navy pilot, and headed east through rainy weather to Okaloosa-Walton College here in Niceville and a later rally in Panama City. At each rally, he was greeted by huge and appreciative audiences. People lined the highway as the president's long motorcade rolled through. Many waved signs of support, with only a few holding dissenting signs.

Florida, the site of a disputed 36-day recount in 2000, remains one of the most competitive states in the country this year. Four years ago, Bush carried the Panhandle counties with huge margins. Kerry advisers questioned why the president was spending time campaigning in such core Republican territory rather than reaching to swing voters in other parts of the state.

"We want to be sure we cover every part of Florida as we are making an effort to cover every part of every battleground state," said Bush campaign adviser Ralph Reed.

McCain refused to be drawn into Tuesday's debate between Bush and Kerry, saying: "I don't pay much attention to the back and forth between the two." Asked in an MTV interview whether he agrees with the Bush campaign criticism of Kerry as a flip-flopper who is soft on defense, McCain replied: "Senator Kerry is a friend of mine. I'm not here to criticize Senator Kerry. I'm here to support President Bush and his reelection, and I think his leadership is needed for the next four years."

Staff writer Jonathan Finer in Las Vegas contributed to this report.

"He has not flinched from the hard choices," Sen. John McCain (R-Ariz.), right, said of President Bush in Pensacola, Fla.