Democratic supporters of a medical innovation bill headed to President Barack Obama's desk say they fear its mental health provisions will be outweighed if Republicans and President-elect Donald Trump are successful at repealing Obama's signature health care law.

Though members of both parties overwhelmingly came together this week to pass the 21st Century Cures Act, a bill that includes provisions to make it easier for patients to access mental health treatment, they also made it apparent their consensus will end when it comes to the Affordable Care Act.

In recent weeks, lawmakers have highlighted Obamacare's contributions to the mental health arena, including that it's given millions of previously uninsured, low-income people access to coverage through Medicaid and has required insurance plans to cover mental health and addiction treatment. The law also expanded upon previous parity regulations mandating comparable mental health and physical health coverage.

The Cures Act given final approval in Congress on Wednesday provides for a new agency position called the assistant secretary for mental health and substance use and directs government health agencies to better define privacy laws so family members can help loved ones receive care. It also expands a grant program for assisted outpatient treatment, or court-ordered care for people with serious mental illness who otherwise might not seek help.

On the House floor last week, Rep. Frank Pallone Jr., a New Jersey Democrat and the ranking member on the chamber's Energy and Commerce Committee, said he was pleased about the bill's mental health provisions but warned they would "be far outweighed by the catastrophic harm caused" by an Obamacare repeal and replacement plan.

Other Democrats agree. Rep. Doris Matsui, D-Calif., says Obamacare's repeal would be "devastating" to progress on mental health.

"If we disrupt the important groundwork we've laid, families will be the ones who feel the impact," she says in an emailed statement.

Most Republicans have not provided specifics about what a replacement plan would look like and how it would involve mental health coverage, though party members have pointed to House Speaker Paul Ryan's "Better Way" outline, which includes proposals that would be tied to mental health services. Among them are encouraging the use of health savings accounts and the potential administration of Medicaid through block grants. It also promises coverage for people with pre-existing conditions.

Rep. Tim Murphy, a Pennsylvania Republican who has championed mental health reform in Congress, says he thinks a replacement plan gives lawmakers the opportunity to improve the country's mental health care services.

"We have worked so hard on [mental health] for four years," he says. "We are not going to let that slide."

Murphy introduced a mental health bill following the mass shooting at Sandy Hook Elementary School in 2012, in which it was later found that the gunman had not received needed treatment for mental illness. After changing his bill to address concerns about patient rights, Murphy's Helping Families in Mental Health Crisis Act was added to the 21st Century Cures measure.

Murphy, a psychologist, says interest in Congress about mental health issues and care has grown, and he is optimistic bipartisanship on related policy areas can be achieved.

On Monday, lawmakers briefly celebrated such bipartisanship in a press conference.

"This legislation shows that there really is nothing political about the issue of treating people with mental illness," said Sen. Chris Murphy, D-Conn., who introduced the Senate's companion to Rep. Murphy's mental health legislation.

But in an emailed statement to U.S. News, the senator says Obamacare's repeal would result in "millions of people across the country who would lose insurance and – overnight – lose access to psychiatrists and psychologists and medications."

Rep. Eddie Bernice Johnson, D-Texas, shared similar thoughts.

"This is the epitome of our institution when we can come together and pass a major piece of legislation that impacts every life ... whether you're a liberal or conservative," she said at Monday's press conference.

"I'm beginning to wonder what I am," she joked.

But Johnson stood firmly with liberals when it came to Obamacare's repeal, also telling U.S. News in an emailed statement it would undo mental health reforms in the Cures Act, "leaving vulnerable and low-income patients back at square one."

With Trump having won the White House, congressional Republicans say they plan to tackle the dismantling of Obamacare as a first order of business next year. The president-elect vowed during his candidacy to repeal and replace the law – a welcome position for Republicans who have been opposed to the bill since its final passage with no GOP support in 2010.

GOP lawmakers are expected to tackle at least part of the repeal effort through a reconciliation bill, a spending-related measure that requires only a simple majority of votes in the Senate and can avoid a Democratic filibuster. The bill may be similar to a measure previously vetoed by Obama that called for certain parts of the law to gradually phase out, including Medicaid expansion.

Andrew Sperling, director of federal legislative advocacy at the National Alliance for Mental Illness, which supported Obamacare's passage, says he expects his group to oppose the law's repeal, though it hasn't made an official statement as it waits to see what legislation is introduced.

"NAMI is already working on a series of positions about what we need to work to protect and retain in a replacement bill," he says, pointing to provisions that mandate health insurance plans cover mental health and addiction treatment, as well as requirements for parity. The group also is opposed to distributing Medicaid funds through block grants.

"We have allies on both sides of the aisle," Sperling says. "But there is still a fairly wide political divide between Republicans and Democrats about the [Affordable Care Act.]."

Others say they aren't concerned.

John Snook, executive director of the Treatment Advocacy Center, which advocates for legislative mental health reform, says he thinks Congress understands the need to address the issue in an Obamacare replacement plan, given how costly treatment for people with mental illness can be.

He also acknowledges that people with severe mental health conditions, such as schizophrenia or bipolar disorder, have been helped through the expansion of Medicaid.

"I think everyone recognizes this crisis," he says. "We don't know yet where things are going to end up."

DJ Jaffe, executive director of Mental Illness Policy Org, also says he is waiting until more details are put forward.

"I am an uber-liberal, but on this issue conservatives tend to be better," he says.

Rep. Murphy says a full repeal and replacement plan will take time.

"Don't think we'll just walk in and repeal and replace and that will be it," he says. "It'll take months to think about, and we'll be looking at how to do it correctly."

He says a Republican replacement plan will include coverage for people with pre-existing conditions, and will allow for the opportunity to create a more transparent system in regard to how states use federal money for mental health services.

He also supports Medicaid being distributed through block grants, and says a replacement plan can make sure funds go toward effective, evidenced-based programs.

Rep. Joe Kennedy, D-Mass., says he thinks mental health reforms under Obamacare didn't go far enough and could be strengthened. He cited research showing insurance companies are skirting parity rules, and called for more enforcement.

"Rolling back Medicaid or essential health benefits will only make it that much harder for families across the country to gain access to behavioral health care we so clearly need," he says.

Kennedy pointed to the fact that patients still struggle to get mental health care because there aren't enough providers, and said many patients have to wait months to see a doctor.