DENVER – Colorado Republican Senator Cory Gardner is threatening not to vote for the bill Republicans in the U.S. House of Representatives have drafted to replace the Affordable Care Act if it isn’t changed ahead of a vote.

Gardner and three other Republican senators – Rob Portman of Ohio, Shelley Moore Capito of West Virginia and Lisa Murkowski of Alaska – sent a letter Monday to Senate Majority Leader Mitch McConnell saying the House draft replacement bill doesn’t adequately cover Medicaid recipients in states that have voted to expand Medicaid under the ACA, also known as Obamacare.

The draft bill was released by House Republicans Monday afternoon. Read it by clicking here.

The letter says the draft “does not meet the test of stability” for people enrolled in Medicaid.

“We will not support a plan that does not include stability for Medicaid expansion populations or flexibility for states.”

The states the four senators represent all voted to expand Medicaid under Obamacare.

“Reform should not come at the cost of disruption in access to health care for our country’s most vulnerable and sickest individuals,” the letter reads. “Any changes made to how Medicaid is financed through the state and federal governments should be coupled with significant new flexibility so they can efficiently and effectively manage their Medicaid programs to best meet their own needs.”

Though the letter says the senators believe the Affordable Care Act should still be repealed and replaced, it also says that a gradual rollout of the new program would be necessary “to ensure states have the time to successfully implement” the new changes.

Medicaid serves mostly low-income and disabled individuals, and the letter sent by Gardner says that he and the other senators fear a “poorly implemented or poorly timed” change in its funding structure would result in a “reduction in access to life-saving health care services.”

The letter also points out that Health and Human Services has noted that one-third of Medicaid recipients covered under its expansion has a mental health or substance abuse disorder.

One in five Coloradans are covered through Health First Colorado, the state’s Medicaid program.

House Republicans are expected to introduce the replacement bill in committee on Wednesday after meeting with the White House Friday and working through the weekend to put finishing touches on the bill.

Gardner had been among several Republicans under fire from constituents worried about losing their health care if the ACA is replaced. But he has also discussed a bill that would defund Planned Parenthood, saying he is pro-life, which has angered some saying he’s on the fence on health care issues.

But during his time in Congress, Gardner voted numerous times in the past to repeal Obamacare or gut the program, according to a health care vote tracking organization.

In the 2014 Senate campaign, Gardner told a woman who asked him about Medicaid expansion that he “didn’t know how” Colorado would pay for it.

At least four Senate Republicans would have to vote against the bill to stall it. Aside from the four who listed concerns about Medicaid, some other Republicans have voiced worry over the use of tax credits to offset individual costs. Republicans hold 52 seats in the 115th Congress, compared to 46 Democrats and two independents who usually vote with Democrats.

The full letter the four senators sent to McConnell can be read below:

Dear Majority Leader McConnell,

As you know, Medicaid covers more than 72 million Americans and is the core of the health care safety net for individuals across the country. The Affordable Care Act destabilized the private insurance market and created an unsustainable path for both the states and the federal government in Medicaid. While we support efforts to repeal and replace the Affordable Care Act and make structural reforms to the Medicaid program, we are concerned that the February 10th draft proposal from the House of Representatives does not provide stability and certainty for individuals and families in Medicaid expansion programs or the necessary flexibility for states.

We are concerned that any poorly implemented or poorly timed change in the current funding structure in Medicaid could result in a reduction in access to life-saving health care services. The Medicaid population includes a wide range of beneficiaries, many of which cycle on and off Medicaid due to frequent changes in income, family situations, and living environments.  The Department of Health and Human Services reports that nearly one-third of individuals covered under the Medicaid expansion have a mental health or substance use disorder. As the largest payer of mental health and substance use services in the United States, it is critical that any health care replacement provide states with a stable transition period and the opportunity to gradually phase-in their populations to any new Medicaid financing structure.

We believe Medicaid needs to be reformed, but reform should not come at the cost of disruption in access to health care for our country’s most vulnerable and sickest individuals. Any changes made to how Medicaid is financed through the state and federal governments should be coupled with significant new flexibility so they can efficiently and effectively manage their Medicaid programs to best meet their own needs. We also believe a gradual transition is needed to ensure states have the time to successfully implement these new changes. The Affordable Care Act is not working for states or the federal government and must be repealed and replaced with a plan that reforms Medicaid and protects individuals and their families over the long term. However, the February 10th draft proposal from the House does not meet the test of stability for individuals currently enrolled in the program and we will not support a plan that does not include stability for Medicaid expansion populations or flexibility for states.

Sincerely,

[Senators]