Senators Bill Cassidy and Lindsey Graham have proposed an alternative health care bill in the most recent GOP attempt to replace the Affordable Care Act. But even Republicans are skeptical of its success.

The bill, H.R. 1628 (115), would replace the tax credit system that Obamacare had in place, instead opting to give states block grants to fund their own healthcare systems. The bill would also replace Medicare expansion and cost-sharing payments, and would completely eliminate a medical device tax and health care mandates.

Conservative groups have spoken against the bill, saying that there needs to be a full overhaul of Obamacare — not just a replacement.

“Real repeal is getting the Affordable Care Act off the books for good,” Twila Brase, president and co-founder of Citizens’ Council for Health Freedom, said. “Americans are long overdue for a true repeal vote. They deserve it.”

Conservative members of the Senate have also spoken out about the bill. Sen. Rand Paul said that he doesn’t see Cassidy and Graham’s bill “going anywhere,” and Orrin Hatch, chairman of the Senate Finance Committee, simply responded “no” when he was asked if he thought the bill would get a vote on the Senate floor, according to The Hill.

Sen. John McCain voted no in July against another “repeal and replace” bill that other Republicans supported. Most recently, McCain has publicly stated that he supports the proposed bill. According to The Hill, when reporters asked him if he would be in favor of the bill, he said, “Yes. You think I wouldn’t be?” Later in the day, McCain backtracked on his earlier comments, saying in a released statement, “As I have said all along, any effort to replace Obamacare must be done through the regular order of committee hearings, open debate and amendments from both sides of the aisle.”

Despite mixed reactions, Cassidy told reporters that he believes that 48 or 49 senators will support the bill when it goes up for vote. The bill only requires a simple majority in order to move forward, and Cassidy said he believes Vice President Mike Pence would vote in favor of the bill, should there be a tie.

Cassidy and Graham have until Sept. 30 to pass the bill, an act that Sen. John Thune, the third-ranking Senate GOP leader, said would need a “double-double bank shot” in order to happen, and would take “extraordinary lift.”