WASHINGTON – Mitt Romney’s campaign fiercely protested a searing attack ad aired by allies of President Barack Obama on Wednesday, but drew expressions of dismay from conservatives when an aide to the former Massachusetts governor invoked the benefits of a state health care system he signed into law.

“If people had been in Massachusetts under Gov. Romney’s health care plan, they would have had health care,” spokeswoman Andrea Saul said in an interview on Fox News. The Republican presidential candidate himself rarely mentions the law, which contains a requirement to purchase health coverage similar to the one in the federal law that conservatives despise and he has vowed to repeal.

Saul volunteered her observation after sharply denouncing the ad. In it, a grim-faced former steelworker, Joe Soptic, suggests that Romney and Bain Capital, the private equity firm he founded, might bear some responsibility for his wife’s death from cancer several years ago.

“It’s just despicable, to be honest,” Saul said of the commercial, which is aired by Priorities USA Action, a super PAC that supports Obama’s re-election. “Of course he doesn’t want to see ill come to anyone.”

Independent fact checkers judged the commercial harshly, sometimes unusually so.

Additionally, the Romney campaign alleged that the president’s campaign “lied repeatedly about its knowledge of the content” of the commercial. The allegations were denied.

Whatever the particulars, conservatives were quick to react to Saul’s remark about the health care law that Romney signed as governor of Massachusetts.

Conservative talk show host Rush Limbaugh excoriated Democrats over the TV spot. But he added that the Romney aide’s remarks were “a potential gold mine for the Obamaites, because they can say, ‘Well, yeah, and Romneycare’s the foundation for our plan, Obamacare,’ which they are already out there saying.”

The back and forth over the commercial largely overshadowed the day’s campaign activities by the president and his challenger.

Romney campaigned in Iowa, where he drew a standing ovation for promising to repeal “Obamacare,” the derisive label that Republicans long ago hung on the law the president won from Congress.

“That doesn’t mean that health care is perfect,” he said. “We’ve got to have some reforms in health care. And I have some experience doing that, as you know.”

Obama was in Colorado, where he embraced the Obamacare tag in an appearance before an audience largely made up of women. “I actually like the name because I do care,” he said.