Senators are warning that major changes to the Medicaid program may not survive the upper chamber, despite an aggressive push from House Speaker Paul D. Ryan to include a substantial overhaul of the program in the Republican measure to repeal the health care law.

In the House, Ryan and House Energy and Commerce Chairman Greg Walden are pushing their colleagues to consider major Medicaid changes on a repeal bill this spring. Those include funding mechanisms like so-called block grants and per capita caps or a cap on Medicaid enrollment for states that expanded the program under the health care law, according to House aides.

Others on Walden’s committee, including Health Subcommittee Chairman Michael C. Burgess said the issue would be the focus of the panel’s work this week. The full GOP conference is expected to discuss the issue Thursday.

The House is taking the lead on the repeal efforts while the Senate focuses on confirmation battles. But several Republican senators are already skeptical that a major overhaul of Medicaid, which covers 73 million low-income individuals, could gain traction in the upper chamber.

“I doubt that there is the political will to do that. I think there is enough internal indigestion people have about [the replacement] of Obamacare,” Nebraska Sen. Ben Sasse told CQ Roll Call.

If the House passes a complex bill overhauling Medicaid, the Senate could retreat on those changes and consider a pared-down version of repeal. Republican leaders are already hinting at the possibility of such an outcome.

“We’re talking to the House and coordinating with them, but it may be that they pass something that we can’t pass over here. So we reserve the right to pass something and send it back,” Senate Majority Whip John Cornyn told CQ Roll Call.

To repeal the health care law, the GOP is using a budget maneuver known as reconciliation that requires only a simple majority vote to pass. However, provisions passed through that process must comply with a strict set of Senate rules.

Republicans have recently coalesced around a plan to include aspects of their health care law replacement in the repeal measure, and House Republicans are pushing for a Medicaid overhaul as part of that effort. Aides say the provisions the House is considering have a much more uncertain future in the Senate. 

Walden on Tuesday spoke to the House GOP conference broadly about his panel’s work on the health care law, including efforts to change how the federal government provides Medicaid funding to the states, according to lawmakers leaving the meeting.

“You’re going to see us move forward on the Energy and Commerce Committee looking at reforms, looking at a better way to provide help to those most in need in our states and the Medicaid population and to allow states to innovate,” Walden told reporters after the meeting. “There are great ideas out there among the states, but right now, they have to come back and beg permission from a federal bureaucrat to be able to do much of anything innovative.”

Kentucky Rep. Brett Guthrie, who chairs an Energy and Commerce working group on Medicaid, said the committee was still grappling with the issue of determining funding levels for the states that did not choose to expand their Medicaid programs under the health care law, compared with those that did. He referenced the nearly two dozen Republican senators whose states chose to expand Medicaid, many of whom have expressed interest in keeping that funding. Thirty-one states plus the District of Columbia broadened Medicaid.

Republicans face immense pressure to outline their strategy to repeal the law, both from GOP voters who have been promised such an action for the past seven years and from the health care industry, which is concerned about the impact the policies — or even the underlying uncertainty — will have on the insurance markets.

But work on the repeal has blown past original Republican plans to pass a repeal bill as early as January. Lawmakers are now aiming to mark up legislation in early March. Any big disagreements could further delay that timeline.

Several House Energy and Commerce Committee members said the panel would release, as early as this week, a discussion document outlining its proposal to overhaul Medicaid. A committee spokeswoman declined to comment. 

One House Republican lawmaker who spoke on background to be candid said the measure to repeal the health care law is complete except for work to change Medicaid.

“I think it’s going to per capita [grants] with flexibility for states to have a waiver for block grants,” the lawmaker told CQ Roll Call. “There will probably be some kind of incentive for states that didn’t expand.”

Burgess said his subcommittee could mark up its reconciliation instructions overhauling the law “in the next several weeks,” but that the week following the Presidents Day recess is “a little quick.”

The amount of people on Medicaid has greatly increased since the last time the GOP attempted to overhaul the program, due in large part to the health care law’s expansion. This presents a major challenge to Republicans, said Joan Alker, executive director of Georgetown’s Center for Children and Families.

“If they do try to restructure the entire Medicaid program, that is going to be a huge battle,” she said in a recent interview. “This is the biggest formula fight Congress is ever going to have, period.”