SEMINOLE, Fla. — President Obama on Saturday began hammering away at the Republican ticket’s plans for Medicare, using a campaign swing through Florida, with its large number of retired and elderly voters, to try to turn the page from anemic employment growth, his biggest weakness, to entitlements, a Democratic strength.
Kicking off a two-day bus tour through this perennial swing state, the president told a rally here that Mitt Romney’s running mate, Representative Paul D. Ryan of Wisconsin, had proposed overhauling Medicare and replacing it with a voucher system that could mean higher costs for beneficiaries.
“Florida, you should know I will never turn Medicare into a voucher system,” Mr. Obama said to rousing cheers from a crowd of 11,000 at St. Petersburg College, Seminole. “No American should have to spend their golden years at the mercy of insurance companies.”
The president’s advisers have indicated that they are eager to re-engage their opponents on their Medicare plan, while the Romney camp would prefer to talk about the economy. A government report on Friday showed that employers had eased up on hiring in August, adding just 96,000 jobs, compared with 141,000 in July. The unemployment rate dropped to 8.1 percent from 8.3 percent, but that was largely because of people leaving the work force entirely.
Mr. Romney has sought to blunt Mr. Obama’s Medicare offensive with attacks of his own, something Obama advisers appeared to await eagerly.
“If they want to have a discussion about who do you trust on Medicare for the next 60 days as their central argument, you know we ought to send them an in-kind contribution,” David Plouffe, Mr. Obama’s senior adviser, told reporters aboard Air Force One on Friday. “We’re happy to have that discussion. We think people trust the president more on Medicare.”
The president grabbed that mantle on Saturday and ran with it. “We will reform and strengthen Medicare,” he told the rally, “but we’ll do it by reducing the costs of health care, not by dumping the costs on seniors.”
For good measure, he threw in several more lines in his stump speech aimed at older people, who he said “are saving an average of $6,000 on prescription drugs because of Obamacare. And by the way, I do care.” That was a reference to the derogatory phrase that Republicans have given his health care overhaul. These days, the president has embraced the label with open arms.
“I like the name ‘Obamacare,’ ” he said. Mr. Romney “says he’s going to repeal it. That’s because Romney doesn’t care.”
With 58 days to go until Election Day, the battle for seven or so fiercely contested swing states has intensified. No state is more crucial than Florida, with its 29 electoral votes and its diverse mix of conservative Southerners, Hispanics, African-Americans and elderly and Jewish voters.
Mr. Obama does not appear to have much of a shot with conservative Southerners, but he is fighting mightily for the rest. That is why his weekend bus tour was straddling the center of the state, in the territory that hosted the Republican National Convention two weeks ago. Mr. Obama won Florida in 2008.
After Seminole, the president traveled up Interstate 4 toward Orlando, with a stop in Kissimmee. On Sunday, he was to head down to Melbourne and then West Palm Beach, ground zero for the Bush-Gore election recount of 2000.
Mr. Romney, a former Massachusetts governor, was focusing his efforts Saturday on Virginia, another state that Mr. Obama captured in 2008 and that he has made a priority in his re-election bid.
At his first stop, in Virginia Beach, Mr. Romney led the crowd in the Pledge of Allegiance, using it as a jumping-off point to criticize Mr. Obama and the Democrats for initially passing a convention platform that did not mention God.
“The promises that were made in that pledge are promises I plan on keeping if I am president, and I’ve kept them so far in my life,” Mr. Romney told the cheering audience. “That pledge says ‘under God.’ I will not take ‘God’ out of the name of our platform. I will not take God off our coins, and I will not take God out of my heart.”
The stop in Virginia Beach and an appearance at the start of the Sprint Cup Series Nascar race in Richmond, is intended to help him shore up his lead among white working-class voters.
Although the president trails Mr. Romney in this crucial demographic, some polls still show Mr. Romney underperforming among those voters. Mr. Romney’s choice of Mr. Ryan as his running mate was also expected to help him win over working-class whites and the Republican conservative base, many of whom were wary of Mr. Romney during the primary contests.
For Mr. Romney, the son of a Detroit auto executive turned Michigan governor, courting working-class voters may be a challenge. He is Harvard educated and has an estimated net worth of more than $200 million.
During a visit to the Daytona 500 this year, Mr. Romney ran into some trouble when he said that while he did not follow the sport as closely as some ardent fans did, he had “some great friends who are Nascar team owners.” His opponents used the comment to portray him as wealthy and out of touch with the concerns of average voters.
Mr. Obama has made repeated campaign stops in Virginia, particularly courting black voters around the Richmond area to try to drive up their turnout. He has also focused on liberal-leaning areas of Northern Virginia.
Besides the on-the-ground campaigning this weekend, the Sunday morning talk shows were on the candidates’ agendas. Mr. Romney was to make his first appearance of the campaign season on “Meet the Press” on NBC, and Mr. Obama and Mr. Ryan were scheduled to appear on “Face the Nation” on CBS.
Helene Cooper reported from Seminole, Fla., and Ashley Parker from Boston and Charlotte, N.C.