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Mitt Romney had an unmistakable message for President Obama on Wednesday: Don’t drag me into this.

The president was in Boston, giving a speech at historic Faneuil Hall and drew on comparisons between the Massachusetts law and the problem-plagued Affordable Care Act.

During his speech, Obama acknowledged the problems with ObamaCare and apologized for his clunky rollout.

“There’s no denying it, right now the website is too slow, too many people have gotten stuck and I’m not happy about it,” Obama said.

Obama, in accounting for the troubled launch of ObamaCare, cited the Massachusetts health care law's slow start in an effort to keep expectations low. Romney, as governor, signed that law in 2006.

But Romney, who as the GOP's 2012 presidential nominee ran in part on repealing ObamaCare, emerged from his post-election private life to counter the White House message.

“In the years since the Massachusetts health care law went into effect nothing has changed my view that a plan crafted to fit the unique circumstances of a single state should not be grafted onto the entire country,” he tweeted. “Beyond that, had President Obama actually learned the lessons of Massachusetts health care, millions of Americans would not lose the insurance they were promised they could keep, millions more would not see their premiums skyrocket, and the installation of the program would not have been a frustrating embarrassment.

“Health reform is best crafted by states with bipartisan support and input from its employers, as we did, without raising taxes, and by carefully phasing it in to avoid the type of disruptions we are seeing nationally.”

Former Romney adviser Cindy Gillespie, who played a lead role in developing the Massachusetts law, also told Fox News she sees no parallels between the two rollouts.

She said the sign-up process in the Bay State went relatively smoothly and was implemented in phases.

In November of 2006, Commonwealth Care enrollment began for the residents that were already enrolled to receive "free care" in Massachusetts hospitals. In February of 2007, the state began enrolling residents with annual incomes between 100-300 percent of the federal poverty level, who would receive subsidies to buy Commonwealth Care plans.

In July of 2007, the market opened for non-subsidized people above 300 percent of poverty level. Gillespie said that, to ensure a smooth rollout, they purposefully did not launch a massive IT system without phasing or piloting. "Our enrollment numbers were tied to deliberative phasing and at each phase the enrollment happened like it was supposed to," she said.

Obama, though, drew parallels on Wednesday.

Jonathan Gruber, a Massachusetts Institute of Technology economics professor who advised both Romney and Obama on the development of their laws, said only 123 paying consumers signed up the first month of the Massachusetts law, with 36,000 coming on by the time penalties kicked in for failing to have insurance.

"That same kind of outcome will happen at the national level, but it will take time," Gruber said in a media call previewing the trip organized by the White House. "We need to be patient and measure the outcomes in months and years, not days and weeks."

While more people did sign up as the deadline approached in Massachusetts, its law never faced high-profile computer woes or such fierce opposition. Even though the federal law was modeled in part on Romney's, the former governor ran against Obama last year on a campaign to repeal the federal version.

While in Boston, Obama also planned to speak at a fundraiser for House Democrats at the home of his former ambassador to Spain, Alan Solomont. About 60 people paid $16,200 to $64,800 to dine on Spanish-influenced fare, to be followed by Red Sox cookies in honor of the World Series game being played in town the same night.

Fox News' Joy Lin and The Associated Press contributed to this report.