THE VILLAGES, Fla. (The Blaze/AP) -- Paul Ryan, a champion of changing Medicare, spoke as a passionate defender Saturday, promising seniors that he and Mitt Romney would save it, and he introduced his mother to voters to drive home the point that the health program "was there for our family" and "we have to keep that guarantee."

The vice presidential hopeful tried to strike a careful balance on a dicey subject in his speech at a sprawling retirement community. The Republican ticket has come under withering criticism from President Barack Obama for Ryan's proposals in Congress to overhaul Medicare. Ryan says Medicare will be protected for people in and near retirement, and he wants to see younger generations offered alternatives to the entitlement.

Obama, campaigning in New Hampshire, was casting the choice Election Day as one between two fundamentally different approaches to the government's responsibility to its citizens and who pays the bill. In an excerpt of his planned remarks, he criticized Romney's tax proposals as "trickle-down fairy dust" that has failed to grow the economy in the past and won't work now.

Ryan took the stage in The Villages with his mother Betty Ryan Douglas, 78, while Romney scheduled a series of fundraisers in Massachusetts. The Wisconsin congressman said he saw Medicare's benefits firsthand as a child when his grandmother, with Alzheimer's, moved in with his family. "My mom and I were her two primary caregivers," Ryan said before shifting to his mother and the promise of Medicare for her.

"She planned her retirement around this promise," Ryan said. "That's a promise we have to keep."

"It's not just a program," he added. "It's what my mom relies on."

He accused Obama of undermining Medicare by cutting billions from the program to devote to expanded coverage under his health care law, and asserted: "We want this debate. We need this debate. And we are going to win this debate.

Older Americans have often resisted changes in Medicare, the federal health care insurance program for people 65 and older, and for the disabled.

The Romney-Ryan ticket is betting that voters' worries about federal deficits and the Democrats' health care overhaul have opened the door for a robust debate on the solvency of Medicare, one of the government's most popular and costliest programs.

In the week since Romney announced Ryan as his running mate, Medicare and Social Security have appeared as a driving issue. Florida, Pennsylvania and Iowa are among the top five states in the percentage of people 65 and over, and all three are closely contested this election.