Mitt Romney mentioned the word Medicare only twice Monday in his first Florida stop in St. Augustine after picking a running mate, but no one doubts it will be a central part of the campaign fight in this must-win state.

“The president’s idea for Medicare was to cut it by $700 billion,” Romney said during a morning rally in St. Augustine. “That’s not the right answer. We need to make sure we can preserve and protect Medicare.”

On his second stop in in West Miami-Dade at El Palacio de Los Jugos, the Republican presidential nominee was greeted by a large, enthusiastic crowd where he gave his standard stump speech — absent a single mention of Medicare or Cuba, typical talking points in Miami’s exile community.

Vice presidential pick Paul Ryan, who advocates fundamentally restructuring Medicare, has introduced the subject of entitlement reform like never before in a presidential race. But the Wisconsin congressman’s plan, bashed as “radical” by Democrats, is risky in senior-heavy Florida.

One in five voters is at least 65 years old. More than half are older than 50. And Romney’s path to the White House is close to impossible without winning here. Losing the Sunshine State, where recent polls show an essential tie, would require Romney to sweep virtually every other battleground to win the White House.

Republicans have a strategy to limit the risk: Accuse President Barack Obama of gutting Medicare to pay for the president’s signature healthcare law — one they dubbed Obamacare.

The tactic could well muddy the waters and minimize backlash against Ryan’s controversial Medicare proposal, but it also could boomerang. Ryan essentially voted to keep the same Medicare cuts as those in Obama’s health plan.

Under the 2011 and 2012 Ryan plans approved by nearly every House Republican, the federal healthcare law would have been repealed almost entirely — except when it came to the Medicare reductions in future reimbursement rates to hospitals and drug and insurance companies.

But where Ryan’s plan banked the $700 billion over a decade, Obamacare took the money from the seniors’ program and spent it on programs to expand access to healthcare.

Republicans say that’s tantamount to “stealing” from old folks.

“We shouldn’t cut Medicare to pay for Obamacare. ... [Obama] cuts the payments that go to Medicare by $700 billion and he uses that to pay for Obamacare,” Romney said in Miami, when asked about charges that Ryan’s budget plan is “radical and extreme.”

Under the Ryan and Romney plans, current Medicare beneficiaries would be unaffected. But those who turn 65 in 2022 would face a dramatically different Medicare system. They would get a voucher-like premium-support system that might not keep pace with healthcare expenses. Independent analysts say it would likely increase future out-of-pocket expenses.

Romney supporters say that increasing the role of private insurers in the health marketplace will increase competition and drive down costs.

“The Democrats were going to try to attack the Republicans based on the Ryan plan anyway. We might as well have its best defender on the ticket,” said Republican consultant Sarah Rumpf.

Ryan had been expected to join Romney in Florida on Monday, but instead the Wisconsin Republican was dispatched to Iowa.