Tierney Sneed contributed reporting.

Support for the Senate bill to repeal the Affordable Care Act is teetering on the edge of collapse, with a third Republican senator threatening to join the two who have already promised to block a vote when the bill comes to the floor.

Sen. Ron Johnson (R-WI) learned from TPM last week that Senate Majority Leader Mitch McConnell (R-KY) was telling moderate Republican senators in closed-door meetings that a future Congress and president will not let the bill’s harshest cuts to Medicaid go into effect.

On Monday, Johnson told reporters he went to the moderate senators in question and confirmed that report, causing him to withdraw his previous support for advancing the bill.

“I was strongly in favor of the motion to proceed before I read the comments by Senator McConnell,” he said. “The ‘don’t worry about it, it’s too far in the future, it’ll never happen.’ I’ve confirmed those comments with the senators they were made to, learned they were largely accurate, and I find those comments very troubling. It really does put in jeopardy the motion to proceed.”

When TPM reached out to McConnell for comment, he replied with a statement that did not specifically refute the accusation. “I prefer to speak for myself, and my view is that the Medicaid per capita cap with a responsible growth rate that is sustainable for taxpayers is the most important long-term reform in the bill,” he said. “That is why it has been in each draft we have released.”

Yet Johnson maintains that besides the alleged doublespeak from leadership, which he called “a real breach of trust,” he also has major problems with the bill itself.

“It’s not the bill I’d write, not by a long shot,” he said, adding that he wants the Medicaid expansion eliminated sooner.

“I want to see additional enrollment ended,” he said. “The fact that we’re not doing that as quickly as we should ramp that down, it’s putting at risk an already unsustainable legacy Medicaid program.”

Johnson’s abrupt about-face seems to be rattling leadership, who cannot afford to lose a single additional Republican vote. Senate Majority Whip John Cornyn (R-TX), when confronted outside the Capitol by reporters asking him to respond to Johnson’s allegation, said to his driver “I think we ought to go,” got into his car, and drove away.

This post has been updated with comments from Majority Leader Mitch McConnell.