AUGUSTA — As Congress begins its debate in Washington, D.C., over the repeal of the Affordable Care Act, a top Maine Democrat is warning that overturning the federal law, known commonly as Obamacare, could cost the state billions of dollars and hurt thousands of people.

“They may promise that a replacement plan will be done, but Maine families and businesses can’t feel comfort with a promise,” said Senate Minority Leader Troy Jackson, D-Allagash, during a press conference at the State House Wednesday. “They need to know what the plan is today, not tomorrow.”

ACA enrollments in Maine are 9 percent ahead of the same time period last year, according to numbers released last week by the U.S. Department of Health and Human Services. About 75,000 Maine residents signed up for Affordable Care Act insurance in 2016, and most receive a subsidy to help pay for premiums.

Jackson and a group of health care advocates in Maine highlighted several key issues on what repealing the federal law, which has been both praised and panned, would mean for Maine, saying that 590,000 Mainers with pre-existing conditions could lose coverage.

Republican President-elect Donald Trump, backed by a Republican-controlled Congress, has vowed to repeal and replace the law that has been considered a hallmark of the administration of outgoing Democratic President Barack Obama.

Forbidding insurers from refusing coverage for people with pre-existing conditions, however, has been a popular aspect of the ACA, with a majority of Americans supporting retaining that feature, and Republican lawmakers and Trump saying they want to keep it. But economists say removing some parts of the law without hurting other parts will be difficult, if not impossible.

Flanked by Andrew Volk, a Portland restaurateur and an advocate for affordable health care, Jackson retold the story of a friend, Ryan Kelly, who died from a heart attack at the age of 29, largely because he didn’t have health insurance, Jackson said, choking back tears.

Jackson, who has previously served in the Legislature, said as of Jan. 1 he was back on government-sponsored health insurance and would likely be dead by now without it, noting that he is on his third pacemaker.

“Today in Washington, a lot of people who also have government-sponsored health insurance are making the decision for the rest of us in this country – who is working, who isn’t working?” Jackson said. “What we need is for people to have that security, that peace of mind, that when they don’t feel right, their family doesn’t feel right, they can go to a hospital and have a doctor look at them.”

Volk, co-owner of the Portland Hunt and Alpine Club, said the Affordable Care Act allowed his wife, Briana Volk, to seek a policy in the marketplace and not worry about leaving her job while she was pregnant in 2013. That allowed her to focus on helping him make their restaurant successful. Andrew Volk said that assurance allowed them to grow the business so they could open a second restaurant, adding 45 jobs to the Portland market.

“When our daughter was born, there were complications that would have cost us tens of thousands of dollars without coverage. Instead, because of the Affordable Care Act, we were able to continue to focus running our business, where we currently employ over a dozen individuals,” Volk said. He said continued coverage under the federal law allowed his family the financial resources to purchase a home and start another business.

Jackson, Volk and Emily Brostek, executive director of Consumers for Affordable Health Care, a Maine-based nonprofit, also urged Mainers to contact the state’s congressional delegation and urge them to not repeal the Affordable Care Act without first creating a replacement that was as good or better.

“The ripple effect of a repeal without a replacement would be irresponsible and felt across the entire country,” Brostek said.

In Maine, 56,270 people had signed up for ACA insurance by Dec. 19. There are no state data on how many are new enrollees, but if Maine hews to the national trend, there would be about 17,500. If trends hold true, by the time the final numbers are counted after the Jan. 31 sign-up deadline passes, Maine will surpass the 75,000 enrollees in 2016 by about 10 percent.

Nationwide, about 6.4 million people have enrolled in ACA insurance for 2017, beating last year’s numbers by 400,000. That does not include automatic re-enrollments. Of the 6.4 million, about 2 million are new customers, according to federal data.

Leading Republicans in Washington, including Speaker of the House Paul Ryan, D-Wisconsin, also vowed Wednesday they wouldn’t repeal the ACA without a replacement.

On Wednesday Vice President-elect Mike Pence confirmed repealing and replacing the law was the top priority for the Trump administration, according the Associated Press.

“The first order of business is to repeal and replace Obamacare,” Pence said, using the overhaul’s nickname. He said Americans “voted decisively for a better future for health care in this country, and we are determined to give them that.”

Jackson said he hoped that would be the case, but intended to propose state law changes that would give consumers some of the same protections in the federal health care law, including prohibitions on lifetime caps or a denial of coverage for pre-existing conditions.

“Half the people in this state are benefiting from that, so I just can’t see the logic in having that pulled away from them,” Jackson said. “So those would definitely be things that I would be including in that.”