President Bush turned his Marine One chopper into a campaign prop Saturday and used it to drop in on huge crowds at three stadiums around Florida, at a time of concern in his campaign about his failure to gain a decisive lead in the most crucial battlegrounds.

Bush's speeches elicited cheers from his fans as the president unleashed 36 or more different attacks on his Democratic challenger, Sen. John F. Kerry (Mass.), who on Saturday added more inspirational rhetoric to his remarks in what his strategists called an effort to finish on a more positive note.

"I ask you to take your hopes with you in these next days," Kerry told 10,000 people at a historic train depot in Pueblo, Colo. "Vote your hopes, not the fears that George Bush wants you to feel."

The commander in chief landed at the ballparks to the strains of the "Top Gun" theme, his most dramatic use of a military asset since he rode a fighter jet onto an aircraft carrier 17 months ago to declare the end of major combat operations in Iraq.

The president is battling to hold on to Florida and Ohio, the two remaining biggest battlegrounds Bush won in 2000. He cannot afford to lose them both. But Kerry is struggling to hold on to several states Al Gore won, including Iowa and Wisconsin. Depending on how they and a handful of other states turn, the election still appears up for grabs.

GOP officials who talked to Bush-Cheney campaign leaders said the leaders have grown more worried about Ohio, Florida and other key states where Bush lacks a lead with just 10 days until the election. A poll by Ohio University's Scripps Survey Research Center, completed Thursday night, found Kerry leading 49 percent to 43 percent among registered voters, with a margin of error of five percentage points.

Sen. Pete V. Domenici (R-N.M.), campaigning with Vice President Cheney in northwestern New Mexico, told the crowd that the GOP ticket will lose the state without a lopsided local victory in San Juan County, because of heavy Democratic activity elsewhere in the state. "Without a huge margin in this county . . . we can't win this election," he said.

One Republican official described the mood at the top of the campaign as apprehensive. " 'Grim' is too strong," the official said. "If we feel this way a week from now, that will be grim."

It was the third time in eight days that Bush had devoted an entire day to campaigning in Florida, and the dramatic stagecraft underscored the conclusion of his aides that -- as in 2000 -- the election will come down to Florida.

During Bush's chopper swing, a huge banner in the outfield of City of Palms Park, in Fort Myers, showed an image of the military helicopter with the slogan "Soaring to Victory." His departing chopper flew over the crowd of 11,000, so close that the president and Laura Bush could be seen waving.

Bush-Cheney spokesman Scott Stanzel said the campaign will reimburse the government a charter rate determined by the White House Travel Office, but he would not disclose the estimate.

Bush, opening his day at the stadium in Fort Myers where the Boston Red Sox hold spring training, said Kerry's position on Iraq "has evolved during the course of the campaign -- you might call it election amnesia."

"We both have records," Bush said over chants of "flip, flop." "I am proudly running on mine. The senator is running from his."

On Saturday, Kerry targeted undecided voters at huge rallies in Colorado and New Mexico, sticking to his dual message of national safety and middle-class economics, and blaming the president for job losses, low wages and health care costs. He made repeated references to "hope," in a direct swipe at the Bush campaign strategy of continually referring to a possible terrorist attack.

The Kerry campaign is building a cautiously upbeat aura around the candidate, and his staff believes Kerry has hit his stride in both his message and his delivery. For the past week, he has been launching his speech with talk of Iraq and the war on terrorism, pledging to keep America safe, but then he quickly moves to domestic issues. His transition from national security to the economy has become one of his greatest laugh lines before partisan audiences.

"A president has to be able to do more than one thing at the same time," Kerry shouted in Pueblo, as people laughed and cheered.

His second laugh line comes when Kerry ridicules Bush for repeatedly saying of his job, during the first debate, that it is "hard work."

"You know, when it comes to jobs, and health care and all these other things in that debate, I kept hearing the president say -- he would lean over the podium and he'd kind of look at you real nice, like -- then he said, 'It's hard work, it's hard work, it's hard work,' " Kerry said. "Well, Mr. President, I'm ready to relieve you of the hard work," he said, as the crowd roared.

Kerry was courting Hispanics in both states. Flanked in Colorado by Senate candidate Ken Salazar and in New Mexico by Gov. Bill Richardson -- both Hispanic -- Kerry urged people to vote, at one point speaking in Spanish.

The other chopper rallies were in Lakeland and Melbourne. Bush's finale was a rally for 25,000 or more at Alltel Stadium, home of the National Football League's Jacksonville Jaguars and site of next February's Super Bowl. Bush spoke from a lectern on the 50-yard line. He arrived amid rock-concert-style smoke and departed to fireworks.

The Republican official said polling for Bush showed him in a weaker position than some published polls have indicated, both nationally and in battlegrounds. In many of the key states, the official said, Bush is below 50 percent, and he is ahead or behind within the margin of sampling error -- a statistical tie.

"There's just no place where they're polling outside the margin of error so they can say, 'We have this state,' " the official said. "And they know that an incumbent needs to be outside the margin of error."

Karl Rove, the White House senior adviser, said Bush will win a solid enough victory that the result will be clear sometime after midnight, although he made no prediction about the margin of victory or the number of states Bush would carry.

"It's going to be a close election, but we have a persistent lead" in national polls, said Rove, who was wearing a "Pennsylvania Victory" cap as he traveled with Bush on Saturday.

Bush officials said they believe they will benefit from many intangibles in Florida, including a large military population, one of the nation's stronger state economies, a vast grass-roots organization and the popularity of the president's brother, Gov. Jeb Bush.

Rove said Bush has begun advertising more heavily in Michigan, a state that once appeared out of reach for Bush, and the White House announced that Bush will stay overnight there in the coming week.

Kerry's running mate, Sen. John Edwards (N.C.), campaigned in Florida and seized on a Fortune magazine report that the Social Security Administration is considering raising the retirement age for full benefits from 65 to 72. Edwards said in Orlando that Bush "says he wants to protect Social Security, but he winks and he nods, and the leaks tell us something different."

Bush-Cheney spokesman Reed Dickens said Bush "is against raising the retirement age, increasing taxes or decreasing benefits."

Romano is traveling with Kerry. Staff writer John Wagner, traveling with Edwards, contributed to this report.

President Bush speaks to supporters at the Florida spring training facility of the Boston Red Sox. He assailed Kerry as the most liberal member of the Senate. Bush aides believe Florida will decide the election, as in 2000. Sen. John F. Kerry reaches out to supporters in Las Cruces, N.M. He stressed domestic issues at huge rallies in New Mexico and Colorado.