The candidates have circled the issue for months, throwing bantam punches that mostly missed. During Thursday night's GOP presidential debate, Rick Santorum broke through with an aggressive dismantling of Mitt Romney on health care.
"Your mandate is no different than Barack Obama's mandate. It is the same mandate," Santorum said. "Folks, we can't give this issue away in this election. It is about fundamental freedom."
Romney until that point had delivered a performance that re-established his claim to the Republican nomination - a goal he could leap toward Tuesday by winning Florida's primary.
But Santorum drew fresh attention to a weakness that has long shadowed Romney. While he rails against "Obamacare," the similarities with the plan Romney implemented as governor of Massachusetts - "Romneycare," as Santorum called it - could deflate a contrast Republicans are eager to draw in the general election with President Obama.
It's easy to imagine Democratic ads juxtaposing Romney's campaign rhetoric with his support of the plan in Massachusetts, which is widely popular among residents, and was a template for the federal law.
"It's the Et tu, Brute strategy," said Alex Castellanos, a national Republican strategist who worked for Romney in 2008. "You try to kill somebody by trying to hug them and get as close as possible. It's smart politics. It just doesn't happen to be true."
Romney says that on his first day as president he would issue an executive order allowing states to opt out of the law and then work with Congress to repeal it. He vehemently points out that his plan was state specific, not a "one-size-fits-all" national mandate.
Still, the parallels could play into the hands of Democrats looking for angles in what could be a significant challenge for their party.
"It has zero effect on me," said Steve Manikowski, 48, of Orlando, who attended a Romney rally Friday night. "My concern is the people who are uninformed, those who make their decisions based upon the sound-bite or a commercial."
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Obama's signature achievement has been a feeding ground for Republicans, who marshaled forces in the 2010 midterm elections to capture the House of Representatives and stunt Democrats in the Senate.
Opposition to the health care law was so powerful it spread to state races, such as Florida's gubernatorial contest, won by Rick Scott, a former health care executive who got his start in politics by opposing the universal coverage Democrats were seeking. Scott campaigned as much against Obama as he did Democrat Alex Sink.
The issue has slipped on the campaign trail as Republican candidates focus on a persistently poor economy and high unemployment. That has kept Romney's strength out front.
But this spring when the U.S. Supreme Court weighs in on the constitutionality of the health care law, Romney could be in a bind. If it is struck down, as Republicans hope, Romney may not be as well positioned to tap into the momentum.
Romney's GOP primary rivals have largely given him a pass, no better illustrated than a debate last summer when then-candidate Tim Pawlenty declined to repeat his charge that the Romney and Obama plans were essentially the same. Pawlenty had even given it a name: "Obamneycare."
Santorum, who has struggled to build on his surprise victory in Iowa's caucuses, yanked the issue back into the spotlight Thursday in Jacksonville. "Those are not the clear contrasts we need if we're going to defeat Barack Obama," he said.
"It's a credibility thing. Republican voters won't see the distinction," said Michael Spencer, 53, who attended a Newt Gingrich campaign stop Saturday in Winter Park.
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There are clear similarities between the Massachusetts plan and the national law.
Both require people to buy insurance or pay a penalty, known as the individual mandate. Both expand Medicaid and give government subsidies for lower-income people to afford health care. Under both plans, most large companies that fail to offer coverage to employees face fines.
Several experts who helped shape the plan signed into law by Romney in 2006 met with White House officials as the federal plan was being developed.
"They really wanted to know how we can take that same approach we used in Massachusetts and turn that into a national model," Jonathan Gruber, an economist, told NBC News.
Romney's campaign has played down the links, and Romney has said that had Obama called for advice, he would have argued against a national model.
Romney stresses that an overwhelming number of Massachusetts residents already had insurance - meaning the plan applied to a small number - and that the plan did not rely on extra taxes on drugmakers, insurers or people who opt for high-cost health care plans.
"In debating Barack Obama, I will be able to show that I have passion and concern for the people in this country that need health care," Romney said in Thursday's debate. "But I will be able to point out that what he did was wrong. It was bad medicine, it's bad for the economy, and I will repeal it."
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Romney's history has contributed to a failure to fully win over conservatives, many of whom are already wary of previous moderate positions on abortion and gay rights.
"It's my one small concern about Romney," said Brock Shields, a 37-year-old lawyer from Orlando. "I don't like the idea of telling people you have to buy something. What if the government says everybody has to buy a Buick because we think it's in your best interest to buy a Buick?"
But he agreed with Romney that the state plan is not on the same scale as the national law. "No one's perfect," he added. "And I do think Romney's got a good plan for America."
Jacob Franklin, 33, of Port Richey said he too warmed to Romney, whom he once considered "a little too liberal," on the strength of his message to turn around the economy.
"I think it's actually a good thing," he said of the health care debate resurfacing in the GOP primary. "He can say, 'I gave the liberal voters in Massachusetts what they wanted and it's failed.' Unfortunately, he's sticking by it."
Even if he does poorly in Florida, Santorum is not going away. He said Friday he will continue his campaign into other states and repeated his criticism of Romney, calling his position "a big, big liability for us going into this general election." (Romney supporters note Santorum backed Romney in 2008, suggesting he's just playing politics.)
Even Gingrich joined in during a stop Saturday in Winter Park, telling voters it would impossible to have a "rational debate" with "Romneycare" resembling the national law.
"It is a clever trap that the Obama campaign lies trying to get Republicans to link them together," said Stuart Stevens, Romney's campaign strategist.
Romney, he insisted, would not shy from the issue: "I think we take on Obama by saying 'Look, you're not going to get away with this.'"
Alex Leary can be reached at firstname.lastname@example.org.