DAYTONA BEACH, Florida (CNN) -- Sen. Barack Obama told voters in Daytona Beach, Florida, on Saturday that if Sen. John McCain became president, he would privatize their Social Security.
It's a debate over the program that could resurface as a major issue in the closing weeks of the campaign, given the wild swings in financial markets.
"If my opponent had his way, the millions of Floridians who rely on it would've had their Social Security tied up in the stock market this week. Millions would've watched as the market tumbled and their nest egg disappeared before their eyes," he said.
"I know Sen. McCain is talking about a 'casino culture' on Wall Street, but the fact is, he's the one who wants to gamble with your life savings, and that is not going to happen when I'm president. When I'm president, we're not going to gamble with Social Security."
The McCain campaign disputed Obama's assertion, calling it "a desperate attempt to gain political advantage using scare tactics and deceit." Election Center: Where the candidates stand on Social Security
Obama also highlighted an article McCain penned in this month's issue of the American Academy of Actuaries magazine, called "Contingencies," in which he said consumers would have more choices for health insurance products if the market was opened to more "vigorous nationwide competition, as we have done over the last decade in banking."
"He wants to run health care like they've been running Wall Street. Well, senator, I know some folks on Main Street who aren't going to think that's such a good idea," Obama said. 
Listen to Obama's Saturday radio address »
The Democratic nominee has one more event in Jacksonville before heading to North Carolina for an event Sunday in Charlotte.
The campaign announced that Obama will spend several days next week in Tampa, Florida -- a spot along the Interstate 4 corridor that is considered a crucial swing vote region for both candidates -- prepping for Friday's first presidential debate.
In a radio address Saturday, McCain blasted Obama's ties to failed mortgage lenders Fannie Mae and Freddie Mac.
"While Fannie and Freddie were working to keep Congress away from their house of cards, Sen. Obama was taking their money. He got more, in fact, than any other member of Congress, except for the Democratic chairman of the committee that oversees them," he added. Fact Check: Did Obama 'profit' from Fannie Mae, Freddie Mac?
Last week, Obama's campaign highlighted the fact that several of McCain's top advisers had lobbied on behalf of the two lenders.
Nonetheless, the McCain campaign released an ad Friday linking Obama to former Fannie Mae CEO Franklin Raines. Watch McCain lash out on Obama's financial plan »
"Who advises him?" the female announcer asks. "The [Washington] Post says it's Franklin Raines, for 'advice on mortgage and housing policy.' "
But on Saturday, Obama debunked those accusations.
"My opponent attacked me for being associated with a Fannie Mae guy who I met once and talked to for maybe five minutes. He did a TV ad saying this guy was my adviser. The guy actually had to send out a letter saying, 'That's not true. I actually don't really talk to the guy,' " Obama said.
And the head of the lobbying shop at Fannie Mae turned around and said, 'Wait a minute. When I see photographs of Sen. McCain's staff, it looks to me like the team of lobbyists who used to report to me.'"
Also Friday, McCain's team fired off an ad about Obama's relationship with Jim Johnson, the former Fannie Mae chairman who resigned as head of the Democrat's vice presidential vetting team after allegations that he had received preferential terms on a mortgage from Countrywide Financial. Watch an analysis of the new political ads »
Meanwhile, McCain will stop by his 50-year class reunion Saturday at the U.S. Naval Academy football game.
The Arizona senator, who often mentions his time as a prisoner of war during the Vietnam era, graduated from the Academy in 1958 along with John Poindexter and Robert "Bud" McFarlane, two consecutive national security advisers under President Reagan who played a role in the Iran-Contra affair.
Also Saturday, a new CNN poll of polls in Michigan suggests that Obama has a 5-point lead over McCain, 47 percent to 42 percent, with 11 percent of voters undecided.
Seventeen electoral votes are up for grabs in Michigan.
The current financial crisis from Wall Street to Main Street will more than likely be a major factor in Michigan, a state dealing with hard economic times.
"The struggling economy could be Obama's trump card," CNN Senior Political Researcher Alan Silverleib noted.
"Obama is doing slightly better in CNN's Michigan poll of polls than in CNN's national poll of polls in large part because Michigan is ground zero when it comes to the country's current economic hardship. The unsettling news from Wall Street over the last few days could play to Obama's advantage, especially in the Rust Belt," Silverleib added. Interactive: CNN's Electoral Map
Michigan has voted for the Democratic candidate in the past four presidential elections, but it was quite close in 2004, with Sen. John Kerry beating President Bush there by just 3 points.
The latest CNN poll of polls is an average of the three most recent surveys in Michigan. They are a Big Ten Battleground poll conducted September 14-17, an EPIC/MRA survey taken on the same days and a Marist poll conducted September 16-17.
CNN's Rebecca Sinderbrand contributed to this report.
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