The Post's Jose DelReal explains why Affordable Care Act architect Jonathan Gruber's year-old comments about the historic law have Republicans so angry. (Jose A. DelReal and Nicki DeMarco/The Washington Post)

Jonathan Gruber might not be a household name, but in the world of health care policy, he's a pretty big deal. And now he's also known as the guy who's credited "the stupidity of the American voter" for the passage of the Affordable Care Act.

An old video surfaced this week of Gruber saying that a lack of transparency was one of the reasons Obamacare got through Congress in 2010. Gruber, a Massachusetts Institute of Technology health economist who's credited as one of the intellectual godfathers of the Affordable Care Act, has apologized for speaking off the cuff, but critics of the law are eagerly highlighting his comments.

That's because of what Gruber represents. He was one of the architects of the 2006 Massachusetts health care law, which became the basis for the ACA, and he helped craft the federal legislation that used a similar scheme of guaranteed coverage, financial assistance and insurance mandates. He was far from the only person who helped shape the ACA, but he has been one of its most vocal academic defenders in the nearly five years since it passed. (And he's the only one to write a comic book about the law.)

It's easy to see why Gruber's comments get pored over by ACA opponents. There's plenty of misunderstanding about what's in the ACA and mistrust of the motivations for passing the law — just recall Nancy Pelosi's infamous line about needing to pass the bill to find out what's in it. So when someone like Gruber, who's supposed to know the law inside and out, seemingly confirms critics' worst suspicions, that makes for a powerful anecdote.

Gruber, who's fiercely intelligent and passionate about the health reforms he helped create, also isn't one to always sugarcoat things.

Earlier this year, a pretty important health policy study showed that the expansion of Medicaid coverage in Oregon was associated with a spike in emergency room visits. The research potentially undercut an argument by supporters of the law who said it would save money since giving more people health insurance meant patients would rely more on primary care providers, rather than expensive trips to the ER. And Gruber, commenting on the study, offered an uncomfortable truth.

"I would view [the study] as part of a broader set of evidence that covering people with health insurance doesn't save money," Gruber told the Washington Post at the time. "That was sometimes a misleading motivator for the Affordable Care Act. The law isn't designed to save money. It's designed to improve health, and that's going to cost money."

You may also remember Gruber from the last presidential campaign, when there was plenty of debate over just how similar Obamacare and Romneycare actually were to one another. It was Gruber who artfully cleared up the confusion. "They're the same f------ bill," he told Capital New York in what became a widely circulated interview three years ago. It's probably what ACA supporters wanted to say all along, but only Gruber went ahead and did it.

His most potentially damaging comments surfaced just over the summer, when Gruber seemingly gave credence to the ACA challenge just taken up by the Supreme Court last week — a challenge that if successful could torpedo the law.

The case revolves around whether residents in states that refused to set up their own health insurance marketplaces should still be able to claim tax subsidies to help them afford their insurance. Opponents say no, Congress intentionally didn't allow that under the law. Democrats say they never intended for people in these 36 states to not have access to the financial assistance.

Here was Gruber again, in January 2012, telling a health-care conference that states refusing to set up their own exchanges would deny their residents premium tax credits. The video wasn't widely viewed until June of this year, but this is what he said at the time:

I think what’s important to remember politically about this, is if you’re a state and you don’t set up an exchange, that means your citizens don’t get their tax credits. But your citizens still pay the taxes that support this bill. So you’re essentially saying to your citizens, you’re going to pay all the taxes to help all the other states in the country. I hope that’s a blatant enough political reality that states will get their act together and realize there are billions of dollars at stake here in setting up these Exchanges, and that they’ll do it. But you know, once again, the politics can get ugly around this.

Here's the video, with these comments near the 31:30 mark:

Critics of the law jumped on those comments as further validation of their challenge to the subsidies in the 36 states relying on the federal-run insurance marketplaces, or exchanges. Gruber later said that he misspoke, and that his own work always assumed all exchanges — whether run by the states or the federal government — would be eligible for subsidies.

Gruber's latest comments have surfaced at an especially inopportune time for the Obama administration. The next enrollment period is approaching this weekend with lowered expectations, just as Republicans reclaimed the Senate and the Supreme Court agreed to hear a new Obamacare challenge that could seriously weaken the law.

The Democrats, realizing how harmful Gruber's latest comments have become, are already out doing damage control. Former Vermont Gov. Howard Dean was on MSNBC's "Morning Joe" today to put distance between Gruber and the health-care law, saying he's not even sure that Gruber ever met with President Obama.

"He's a consultant, not the architect [of Obamacare," Dean said. “I’m not excusing the language — it’s terrible."