A bipartisan group of governors urged Senate leaders Tuesday against considering the latest attempt to repeal and replace the Affordable Care Act, calling instead for a bipartisan effort to improve the existing law.

In a letter to Senate Majority Leader Mitch McConnell (R-Ky.) and Senate Minority Leader Chuck Schumer (D-N.Y.), 10 governors said the bill, sponsored by Republican Sens. Bill Cassidy (La.) and Lindsey Graham (S.C.), should be abandoned in favor of legislation written via a bipartisan, open process.

“We ask you to support bipartisan efforts to bring stability and affordability to our insurance markets. Legislation should receive consideration under regular order, including hearings in health committees and input from the appropriate health-related parties,” reads the letter.

“Improvements to our health insurance markets should control costs, stabilize the market, and positively impact coverage and care of millions of Americans, including many who are dealing with mental illness, chronic health problems, and drug addiction.”

The letter is signed by five Democrats (Colorado Gov. John Hickenlooper, Montana Gov. Steve Bullock, Pennsylvania Gov. Tom Wolf, Virginia Gov. Terry McAuliffe and Louisiana Gov. John Bel Edwards), four Republicans (Ohio Gov. John Kasich, Nevada Gov. Brian Sandoval, Massachusetts Gov. Charlie Baker and Vermont Gov. Phil Scott) and one independent (Alaska Gov. Bill Walker).

Maryland Gov. Larry Hogan, a Republican, also opposed the bill in a separate letter, arguing the funding cuts will “directly jeopardiz[e]” his citizens’ health care.

Cassidy-Graham, as the bill is known, is the latest attempt by GOP senators to push through a repeal bill before Sept. 30, the last day the Senate can pass a health care bill with a simple majority.

The bill got almost no public scrutiny until the last week or so, nor has it gone through the normal congressional committee process. And because its Republican backers are hoping to vote by next week, the Congressional Budget Office won’t have time to produce a complete analysis of the legislation — meaning senators won’t know how much premiums will cost or how many people will have insurance under the bill before voting on it.

While the exact effects are unknown, it’s still likely this bill would result in millions of Americans losing their health care coverage. The legislation would eliminate Obamacare’s subsidies as well as that law’s funding for Medicaid expansion by 2020. Instead, states would receive block grants to use as they see fit to help their low-income residents get coverage. States would no longer be required to follow key Obamacare regulations that guarantee coverage for people with pre-existing conditions as well as coverage for maternity, mental health and other key benefits.

According to a preliminary analysis by the Center on Budget and Policy Priorities, the bill would reduce federal spending on health care by roughly $400 billion over the next decade. The legislation would also enact Medicaid cuts, in addition to ending Obamacare’s expansion of the program.

Proponents of the bill argue that the block grant model will give states more flexibility to run their own health care systems. Some analysts, however, have said that because the funding isn’t adjusted for actual coverage costs or enrollment numbers, many states (particularly those where Obamacare has worked best, such as New York and California) will see severe cuts over time. According to the CBPP analysis, 42 states plus the District of Columbia would experience net funding cuts by 2026.

So far, the same three senators who killed the last attempt to repeal the Affordable Care Act remain the key potential swing votes — GOP Sens. Susan Collins (Maine), John McCain (Ariz.) and Lisa Murkowski (Alaska). A fourth Republican senator, Kentucky’s Rand Paul, has already said he opposes the bill. Without him, Republican leaders need to win over two of the other three senators.

The governors’ letter may prove influential in how those three senators vote.

Walker’s opposition, for example, could give Murkowski political cover (or new reason) to vote “no” on the bill. Collins, meanwhile, seems the most likely to vote against the bill, but hasn’t yet given a firm answer as to where she stands.

Of course, gubernatorial influence has its limits. McCain has said he’s still unsure and has raised concerns with the rushed process, even though Arizona Gov. Doug Ducey (R) endorsed the bill Monday.

Kasich, who along with Hickenlooper has previously called for bipartisan reforms to shore up the insurance markets, is a key signatory of the letter, as Sen. Rob Portman (R-Ohio) also hasn’t backed the bill yet. However, Kasich also spoke out against July’s “skinny repeal” plan, which Portman ultimately voted in favor of.