WASHINGTON (NewsNation) — President Barack Obama returned to the White House Tuesday for the first public event since he left office in 2017, to mark the 12th anniversary of his signature health care law, the “Affordable Care Act.”

The ACA, or Obamacare, has become intertwined into the fabric of the American health care system, with current President Joe Biden looking to expand its reach. Sign-ups under the health law have increased under Biden’s administration, and more generous taxpayer subsidies have cut costs for enrollees, albeit temporarily.

Obama’s last time in the mansion was Jan. 20, 2017, when he left to escort his successor, Donald Trump, a president-elect bent on overturning “Obamacare,” to the Capitol to be inauguration.

“It’s good to be back in the White House. It’s been a while,” Obama said in the East Room after he was introduced by Vice President Kamala Harris. He opened by referring to Biden as “vice president” before acknowledging the joke and embracing his former No. 2.

“The ACA was an example of why you run for office in the first place,” Obama said, calling it the “high point of my time here.”

Biden and Obama marked the 12th anniversary of the law, which back in 2010 the then-vice president had memorably called a “big (expletive) deal.” Its staying power has been enhanced by three Supreme Court victories and an emphatic thumbs-down vote by the late Sen. John McCain, R-Ariz., which took the wind out of Trump’s efforts to repeal and replace it.

The Biden administration unveiled a measure Tuesday to fix an element of the ACA, known as the “family glitch.” The quirk is estimated to be keeping about 5 million people from getting coverage under the law.

People tripped up by the family glitch are dependents of workers who have an offer of employer coverage that the government interprets as being affordable. As a rule, people with affordable employer coverage are not eligible for taxpayer-subsidized ACA plans.

But the issue with the current interpretation is that affordability is determined by the cost for employee-only coverage, and not more expensive family policies. Workers able to afford their own share may not be able to cover premiums for the entire family. So the family is cut out of ACA coverage.

The intent of the original policy was to prevent people with employer coverage from going into the health law’s subsidized markets, but advocates say it has proven too restrictive.

The White House estimates that the fix would help 200,000 people get insurance and bring costs down for nearly 1 million more.

In addition to talking health care at the White House, Biden and Obama met for lunch, recalling their weekly ritual when Biden served as Obama’s vice president.

“They are real friends, not just Washington friends,” said White House press secretary Jen Psaki.

Obama likes to refer to his health care law as a “starter home” that Americans can build upon, gradually reducing the 9% share of the population that remains uninsured. The rate was nearly 15% in 2013, before the coverage provisions of the law took effect. Between the health law’s Medicaid expansion and its health insurance markets, more than 30 million people are now estimated to be getting coverage.

Shortly after taking office, Biden opened up the health insurance markets to anyone seeking coverage during the COVID-19 pandemic, and his coronavirus relief bill provided a significant, though temporary, increase in financial assistance. The result was a record 14.5 million people signing up for subsidized private coverage.

Focusing on health care has helped Democrats politically in the past. Obamacare was one of the former president’s top legislative accomplishments, and Republicans have repeatedly tried and failed to repeal it. This comes amid low approval ratings for Biden seven months out from the midterms.

A new NewsNation/Decision poll of more than 1,000 registered voters found that more than 35% strongly disapproved of the way Biden was handling his presidency. You can read the full poll here.