In the five years since the state's landmark health care initiative was signed into law, it has served as a blueprint for national health care, a political football in last year's elections and a talking point in the 2012 presidential contest.
The law also has quietly extended health coverage to hundreds of thousands of Massachusetts' 6.5 million residents who would otherwise be forced to seek health care in emergency rooms or forgo it altogether.
More than 98 percent of Massachusetts residents currently have insurance, the highest in the country, with 400,000 of those being signed up as a result of the law, many of them under a subsidized health plan created by the law known as Commonwealth Care. Among children, the rate is 99 percent.
Still, deep problems remain.
One of the biggest threats to the law is cost. When lawmakers passed the bill, they decided to focus first on expanding health care to as many residents as possible before figuring out the best way to pay for it.
That debate - how to slow soaring health premiums - is now gripping Beacon Hill. Democratic Gov. Deval Patrick has filed a bill he said would ease those premium increases by rewarding doctors and hospitals for the quality of care, not the quantity.
But supporters of the law say that the question of cost shouldn't overshadow the law's accomplishments - top among them the fact that Massachusetts has become a national leader in making systemic changes to what they say is an otherwise untenable health care system.
"What it is, above all, is not an abstract public policy, it's about people and about the kind of commonwealth we want to live in," Patrick said Monday. "I'm very proud of it, and I'm proud to live in a state that believes health is a public good."
Critics also point to what they say are the law's onerous penalties under the so-called "individual mandate," which requires nearly everyone in the state to be insured or face tax penalties.
This year, the tax penalty for adults over age 27 who earn more than $32,496 annually and are deemed able to afford health care but refuse is $101 each month, or $1,212 for the year, or half the cost of the lowest-price private health care plan offered through the law.
In 2008, penalties were levied against 55,000 taxpayers - 30,000 for the full year, 25,000 for part of the year. No statistics were yet available for 2009, officials said.
A similar individual mandate has been included in the federal health care law pushed by President Barack Obama, and that has fueled a political backlash against former Republican Gov. Mitt Romney, who signed the Massachusetts law in 2006.
The national health law and its individual mandate are deeply unpopular with Republican voters.
Romney, who on Monday announced he was forming an exploratory committee as he weighs a run for president, has defended the Massachusetts law even as he has vowed to repeal the national law if elected president.
Romney argues that while the law he signed may be right for Massachusetts, it should be left to states and not the federal government to extend health care coverage.
Earlier this month, speaking to an audience in Las Vegas, Romney gave his strongest defense of the state law and individual mandate, which he said was intended to discourage "free riders" - people who can afford health care but don't obtain it and rely instead on emergency room care, passing the costs onto others.
"We said, you know what, this free-rider problem is a real concern, and so we're going to insist on personal responsibility. We're going to say that people that have the ability to pay should pay for themselves," he said. "We as a state took on a state problem."
Democrats, including Obama and Patrick, have seized on what they perceive as a weak spot for Romney among Republican primary voters by heaping praise on his support of the Massachusetts law.
Democrats are planning to continue that initiative on Tuesday, the five-year anniversary of the bill's signing.
In Massachusetts, the Democratic Party is holding a Romney "Thank You Party" complete with a cake. New Hampshire Democrats are inviting supporters to send Romney a thank you note through Twitter.
And in Iowa, Democratic Party Chairwoman Sue Dvorsky is holding a press conference to "thank Romney for providing the critical momentum necessary to get President Obama's vision of health reform through Congress and signed into law."
This program aired on April 12, 2011. The audio for this program is not available.