Republican centrist senators who have participated in negotiations on crafting a bipartisan healthcare bill have been among those targeted and pressured by political and business interests during the August recess, Sen. Max BaucusMax BaucusTrump has yet to travel west as president Healthcare profiles in courage and cowardice OPINION | On Trump-Russia probe, don’t underestimate Sen. Chuck Grassley MORE (D-Mont.) claimed Friday.

Baucus, the chairman of the Senate Finance Committee and leader of the so-called "group of six" senators negotiating a reform bill, said that the three Republican members of that group have been under tremendous pressure from their own party.

"The Republican leadership in the Senate and in the House is doing its utmost to kill this bill," Baucus told the editorial board of the Helena Independent Record. "They are putting intense political pressure on Chuck GrassleyChuck GrassleyWhite House clarifies: We condemn all violence Republican lawmakers criticize Trump response to Charlottesville Grassley reverses ‘expectation’ of Supreme Court vacancy this year MORE, Olympia Snow and Mike EnziMike EnziSenate panel might not take up budget until October Debt group urges GOP chairman to avoid budget 'gimmicks' Fiscal hawks call for ‘mini-bargain’ on budget MORE, to bow out, because they want to kill it."

Baucus pointed specifically to the prospects of his committee's ranking member, Sen. Grassley, potentially facing a primary challenge next year over his work on the healthcare bill.

"He knows a lot of the opposition against him is orchestrated," he said. "I don't know this, but I strongly suspect they're going to Iowa, they're trying to stir things up to get somebody to run against Chuck in the primary."

Baucus said he doesn't believe that Grassley would abandon the negotiations, but offered words of sympathy for the Iowa Republican and the other two senators working on putting together a bill.

"I know it's easy for me to say right now, because I'm getting beat up by both sides, but not nearly as much as you are by the Republican hierarchy," he said.