Sen. Lindsey Graham of South Carolina. Thomson Reuters

Republican Sen. Lindsey Graham told CNN on Thursday that "there will be holy hell to pay" if President Donald Trump fires Attorney General Jeff Sessions, and he added that it could be "the beginning of the end" of Trump's presidency if Trump goes after Robert Mueller, the special counsel leading the FBI's Russia investigation.

Asked for his reaction to Trump's public criticism of Sessions in recent days, Graham said the president's "effort to basically marginalize and humiliate the attorney general is not going over well in the Senate" or in "the conservative world."

"As a human being, I think he should show respect for Jeff Sessions as a person," Graham said. "Jeff Sessions was the most loyal supporter of Donald Trump."

"If you believe Jeff Sessions should be fired, use the power you have and accept the consequences," he added. "I hope it stops."

Graham, who sits on the Senate Judiciary Committee, added that "there will be no confirmation hearing for a new attorney general in 2017" and that if Sessions is fired, "there will be holy hell to pay."

Political analysts have said Trump — who has expressed anger with Sessions for recusing himself in March from the investigation into Russia's election interference and whether the Trump campaign colluded with Moscow — appears to be backing Sessions into a corner with the hope that he will resign.

According to the news website Axios, Trump recently asked a longtime political associate what would happen if he fired Sessions, whom he has publicly called "beleaguered."

Attorney General Jeff Sessions. AP Photo/Alex Brandon

The Washington Post reported on Wednesday night that Trump had been mulling a possible recess appointment to replace Sessions that could bypass Senate confirmation. Sen. Ted Cruz of Texas and former Mayor Rudy Giuliani of New York were reportedly being considered earlier this week.

Some have speculated that Trump wants to fire Sessions so he can appoint someone who is not recused from the Russia investigation. That appointee could then dismiss Mueller, who is leading the FBI's investigation into Russia's election interference and possible collusion between Trump and Moscow.

Trump is wary of Mueller's examination of his business dealings, and he has reportedly become so disturbed by the path Mueller's investigation seems to be going down that he and his legal team are searching for ways to discredit and possibly fire him. But experts say there is no evidence that Mueller has engaged in any inappropriate behavior that would warrant his removal.

Graham, for his part, said "any effort to go after Mueller could be the beginning of the end of the Trump presidency, unless Mueller did something wrong."