Sen. Lindsey Graham (R-S.C.) offered a forceful warning to Republican colleagues during a private lunch on Wednesday, saying former President Trump will come down hard on any GOP senators who vote for Senate Minority Leader Mitch McConnell's (R-Ky.) deal to set up a special pathway to raise the debt limit.
In blunt remarks to the Senate Republican Conference, Graham harshly criticized McConnell for putting Senate Republicans in position to get "shot in the back" over the deal.
He said McConnell had backed away from his vow earlier this year to not give Democrats any help in raising the debt limit.
One GOP senator said Graham specifically warned colleagues that "the president is going to be engaged on this issue."
He told colleagues that McConnell had "led them on a charge up a hill and they were getting shot in the back," according to the senator.
A second person familiar with Graham's remarks confirmed the comment.
Other Republican senators who heard the remarks said it was unclear from Graham's analogy whether McConnell was to blame for senators getting shot in the back but agreed that his comments were highly critical of the GOP leader's handling of the debt limit standoff.
Graham on Wednesday declined to comment on the details of what he told fellow Republican senators at lunch, though he told The Hill that he disagrees with McConnell's decision to cut a deal with Senate Majority Leader Charles Schumer (D-N.Y.) to create the special legislative pathway on the debt limit.
"I think this is a mistake, but we'll see what happens," he said. "We've been telling our Republican base for four months, '[Democrats] are spending money by themselves, they should raise the debt ceiling by themselves through reconciliation.' "
Graham said "a lot of people believe that changing the rules so they can do it without reconciliation is helping."
"It's pretty obvious to me that this will not be received well by the Republican faithful, including Donald Trump," he added.
Trump issued a blistering statement Wednesday evening that slammed McConnell for agreeing to a special process for raising the debt limit with a simple majority.
"Mitch McConnell just folded on the Debt Ceiling, a total victory for the Democrats - didn't use it to kill the $5 Trillion Dollar (real number!) Build Back Worse Bill that will essentially change the fabric of our Country forever," Trump said in a statement released through his political action committee.
"The Old Crow is a disaster!" he fumed, using his favorite nickname for the GOP leader.
Graham's warning could make it more difficult for McConnell to secure the 10 votes needed from the GOP for a vote on the deal on Thursday.
GOP senators said that earlier this week they believed that McConnell thought as many as 18 Republicans would vote for the bill, which would both stop a scheduled cut to Medicare while setting up the pathway for Democrats to raise the debt limit by a simple majority vote.
But now it looks like it's going to be a scramble to round up 10 Republican votes - the bare minimum - to overcome a filibuster against the proposal, GOP senators said.
"Somebody needs to get to Donald Trump and tell him to shut up about this," said one nervous Republican lawmaker, who added that Graham's warning about Trump is having a chilling effect.
"Graham was warning us about Trump was going to do and 'May God have mercy on your souls,' " the lawmaker said.
McConnell on Wednesday defended his strategy. He argued on the Senate floor that once Republicans vote with Democrats on a bill to establish a special legislative pathway to raise the debt ceiling, Democrats will be forced to do the deed entirely on their own.
Under the deal, Speaker Nancy Pelosi (D-Calif.) and Schumer will have to move a bill that raises the debt limit by enough money to cover federal spending until after the 2022 midterm elections. That means Democrats will have to vote for a bill to increase the debt by another $2 trillion or more - a politically tough vote that will hurt vulnerable Democratic incumbents.
"The whole country understands that Democrats own this mess. They have seized one-party control of the economy, so you better believe they'll have one-party accountability for the resulting nightmare," McConnell argued on the Senate floor.
"Every single Senate Democrat will have to put their name to the gigantic dollar amount of debt they're prepared to pile on the American people," he added.
But Graham is warning GOP colleagues that this argument will not pass muster with Trump and Republican base voters.
"When you tell people you're going to do one thing and you don't, it never ends too well," Graham said Wednesday, referring to McConnell's repeated statements warning that Republicans would not help Democrats raise the debt limit.
McConnell warned President Biden in an Oct. 8 letter that Republicans would not again provide any assistance to raise the debt limit. He sent the missive a day after he and 10 other GOP senators voted for a procedural motion to advance a short-term debt limit increase to an up-or-down vote.
"I will not provide such assistance again if your all-Democrat government drifts into another avoidable crisis," he wrote.
While McConnell believes the special pathway will force Democrats to vote by themselves to increase the debt limit, critics such as Graham think that setting up the pathway is a form of assistance.
Sen. Rick Scott (R-Fla.), the chairman of the National Republican Senatorial Committee and a member of McConnell's leadership team, said Wednesday he would not vote to create the special pathway because he doesn't want to give Democrats any help to raise the debt limit.
"I'm not voting for the debt ceiling increase," he said. "It's really frustrating. Democrats want to go spend all this money but they don't want the responsibility to raise the debt ceiling. I don't actually believe we ought to raise the debt ceiling. I think we ought to figure out how to live within our means."
Trump has called on Senate Republicans to fully leverage their power in the debt limit debate to attempt to stop Biden's sweeping climate and social spending bill.
While Trump's scathing warnings are fuzzy about how exactly that threatening a federal default might bring Biden's agenda to halt, he has made it clear that he thinks McConnell made a big mistake by agreeing in October to a two-month extension of the nation's borrowing authority.
A couple of Republican senators who voted on Oct. 7 for a procedural motion to advance a measure that raised the debt limit by $480 billion - Sens. Richard Shelby (R-Ala.) and Mike Rounds (R-S.D.) - say they won't vote on Thursday to create a special pathway to allow Democrats to pass a bigger debt limit increase with 50 or 51 votes.