The nation’s opioid epidemic is looming over the Senate’s effort to repeal Obamacare.

Senators from states that expanded Medicaid under the Affordable Care Act are worried about the fate of their residents, especially those affected by the opioid crisis. The trepidation is a big hurdle right out the gate for Senate Republicans working on their own Obamacare repeal legislation after the House passed a bill earlier this month.

“We’re just trying to make sure that at a time we are facing this crisis, we are not making things worse,” said Sen. Rob Portman, R-Ohio.

That crisis was responsible for 33,091 deaths in 2015, or 91 a day, with opioid overdoses quadrupling since 1999, according to the Centers for Disease Control and Prevention.

Portman’s state had one of the highest rates of opioid overdose deaths in 2015, with nearly 30 people per 100,000 dying of an overdose, according to CDC data.

About 700,000 people in Ohio took advantage of Obamacare’s Medicaid expansion, and Portman said mental health and substance abuse account for about 50 percent of the costs of the expansion.

The expansion extended the eligibility for Medicaid up to 133 percent of the federal poverty level, with the federal government picking up the entire tab for three years and then shifting some of the cost to the states.

In 2015, about 14 million people in the 31 states that adopted the expansion received Medicaid coverage, according to data from the nonpartisan Kaiser Family Foundation.

“This is a group of people who have been particularly impacted by the grip of this addiction,” Portman told reporters. “Our concern is that we have to have a soft landing to ensure that states can pick up the slack and continue to provide coverage.”

But what that “soft landing” will be is a major question facing the GOP Senate conference.

Portman will play a pivotal role. A 14-member Senate healthcare working group has tasked Portman and Sen. Pat Toomey, R-Pa., with reaching a compromise on what to do about Medicaid.

During the working group’s initial meeting, major disagreements remained on how Medicaid spending should grow, according to an aide familiar with the discussions.

Portman is representing Republicans who want a higher Medicaid spending rate and Toomey conservatives who want a slower one.

Other Republicans more supportive of the expansion include Sen. Shelley Moore Capito, R-W.Va., whose state has been hit hard by opioid abuse. More than 864 West Virginians died from drug overdoses in 2016, according to the West Virginia Health Statistics Center.

“I see a lot of benefits to the Medicaid expansion in our state, particularly in the mental health and opioid and drug abuse area,” Capito told Morning Consult last week.

The Medicaid expansion covers 180,000 people in West Virginia.

The wariness of Capito and Portman compound the Senate’s problem with drafting its own version of Obamacare repeal.

The House bill, the American Health Care Act, that passed earlier this month would cut Medicaid by $880 billion through 2026. The bill would keep the Medicaid expansion until 2020 and then freeze new enrollment. Then states would have to adopt a per-capita cap or block grant funding plan.

While anyone who is covered currently under the expansion would continue to have Medicaid under the House legislation, new enrollees would be out of luck. Another threat is that any state that adopts a block grant or per-capita cap system could change eligibility requirements, forcing some people who have coverage to lose it.

Sen. Bill Cassidy, R-La., practically dared Republicans to adopt any changes that would roll back coverage for people who got Medicaid under the expansion. He said Trump’s contract with voters during the campaign said that nobody who had coverage now would lose it.

Cassidy and Maine Republican Sen. Susan Collins authored their own bill that lets states continue to keep Obamacare and the Medicaid expansion if they want. Or a state could choose another type of insurance expansion or no expansion at all.

“To think you could cut $800 billion as the House bill did and still continue coverage as the president promised is not compatible,” he said.