“Inexcusable” was the word of the day on Capitol Hill.

Both MIT economist Jonathan Gruber and CMS Administrator Marilyn Tavenner invoked it to describe their actions during a more than four-hour hearing Tuesday before the House Oversight and Government Reform Committee.

Ms. Tavenner apologized for including nearly 400,000 dental-only plans in the tally of health insurance enrollments through the state and federal exchanges during a previous appearance before the committee. “It was an inexcusable mistake,” Ms. Tavenner said. “It should not have happened in the first place.”

Mr. Gruber sought penance for a series of videos in which he spoke in extremely injudicious terms about the passage of the Patient Protection and Affordable Care Act. Most notoriously, Gruber stated that Democrats exploited the “stupidity of the American voter” to shield the costs of the law and gain support.

“I behaved badly, and I will have to live with that, but my own inexcusable arrogance is not a flaw in the Affordable Care Act,” Mr. Gruber testified. “The ACA is a milestone accomplishment for our nation that has already provided millions of Americans with health insurance.”

Republicans were unimpressed by the displays of contrition. Mr. Gruber, who served as a consultant for both Obamacare and Romneycare in Massachusetts, drew the lion's share of wrath from legislators.

“Are you stupid?” asked Rep. Darrell Issa (R-Calif.), the outgoing chair of the oversight committee. “Does MIT employ stupid people?”

Not surprisingly, Mr. Gruber did not answer the question directly. Instead he repeated that his comments were inappropriate.

While the proceedings were largely an exercise in political browbeating, one aspect of Mr. Gruber's comments could have ramifications for the federal healthcare law. In 2012, he indicated that residents of states that failed to establish their own exchanges wouldn't be eligible for subsidies to help pay for insurance.

That issue is the crux of the King v. Burwell case that the Supreme Court plans to review next year. If the justices side with the plaintiffs, the ruling could invalidate subsidies for millions of people who live in the 34 states that don't have their own exchanges. Mr. Gruber's comments have been cited in court filings as evidence that the government intended to only provide financial assistance to residents of states with their own marketplaces.

But Mr. Gruber said his statement has been taken out of context and pointed out that every financial model that he ran related to the Affordable Care Act was based on the assumption that subsidies would be available in every state.

“The point I believe I was making was about the possibility that the federal government, for whatever reason, might not create a federal exchange,” Mr. Gruber said. “If that were to occur, and only in that context, then the only way that states could guarantee that their citizens would receive tax credits would be to set up their own exchange.”

Ms. Tavenner was also pressed on the possibility that exchange subsidies could be withdrawn in roughly two-thirds of the states. Rep. Jim Jordan (R-Ohio) questioned why exchange customers aren't being informed about that risk when they sign up for coverage. “Do you think it is at all responsible not telling them that things could change dramatically?” Rep. Jordan asked.

“This is not a closed case, and I'm not going to speculate,” Ms. Tavenner responded. “Nothing has changed for consumers.”

Republicans spent much of the hearing interrogating Mr. Gruber about contracts that he received from the federal and state governments as a consultant on the law and the insurance exchanges. Mr. Gruber was awarded roughly $400,000 from HHS and received similar amounts from at least eight states. But he declined to provide a detailed accounting, repeatedly invoking the advice of his attorney to avoid the question.

Republicans threatened to use the committee's subpoena power to force him to provide the information. “It's really your choice,” Rep. Issa said. “We find your submission deficient.”

Democrats joined in with the castigation of Mr. Gruber's comments. But Rep. Elijah Cummings (D-Md.), the ranking minority member of the committee, also argued that the hearing was a sideshow that provided little insight as to whether the federal healthcare law is fulfilling its purpose.

“This is maybe good political theater,” Rep. Cummings said, “but it will not help a single American get health insurance.”

Paul Demko writes for Modern Healthcare, a sister publication of Business Insurance.