The Supreme Court opinion written by Chief Justice John Roberts made clear that for purposes of the ruling, the mandate amounted to a tax. It noted the mandate differed from an income tax or property tax assessed to broad groups for particular activity, and in this case was a penalty for a lack of activity.
The health care law's "requirement that certain individuals pay a financial penalty for not obtaining health insurance may reasonably be characterized as a tax," the opinion said, adding that "because the Constitution permits such a tax, it is not our role to forbid it, or to pass upon its wisdom or fairness."
On Thursday, the Romney campaign insisted it is Obama who must clarify his stance, saying the president's insistence that the provision is a penalty is at odds with the Supreme Court ruling.
Romney told CBS that regardless of the questions about the mandate, Obamacare is "a lousy piece of legislation" that needs to be repealed.
He has promised to launch a repeal effort on his first day in office if elected but said Thursday he supported some of the most popular provisions of the Obama law -- such as preventing denial of coverage for people with pre-existing conditions and allowing those up to age 26 to stay on family policies.
"These things are available in the marketplace and do not require Obamacare," Romney said.
Obama and Democrats, meanwhile, insist that regardless of semantics, the Supreme Court ruling settled the question of the health care law's constitutionality and now it was time to move ahead on fully implementing it instead of continuing to fight the same political battles.
"I'll work with anybody who wants to work with me to continue to improve our health care system and our health care laws, but the law I passed is here to stay," Obama said to cheers Thursday at a campaign event in Ohio.