GOP Sen. Lindsey Graham Lindsey Olin GrahamGraham: GOP will confirm Trump's Supreme Court nominee before the election Fox's Napolitano: Supreme Court confirmation hearings will be 'World War III of political battles' Grassley, Ernst pledge to 'evaluate' Trump's Supreme Court nominee MORE (S.C.) is warning President Trump that any move to fire Attorney General Jeff Sessions Jefferson (Jeff) Beauregard SessionsGOP set to release controversial Biden report Trump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status MORE will spark backlash from lawmakers.

"If Jeff Sessions is fired, there will be holy hell to pay," Graham told reporters on Thursday morning.

Graham added that Trump's public criticism of Sessions is an effort to "marginalize" and "humiliate" the attorney general. The president's actions aren't "going over well" with his former colleagues, according to the senior Republican senator.

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Graham also warned Trump against firing special counsel Robert Mueller, who is investigating any potential connections between the Trump campaign and Russia. Graham warned it "could be the beginning of the end of the Trump presidency."

Trump has stepped up his public criticism of Sessions, a former GOP senator and his first public supporter in the Senate. He has also warned that Mueller has multiple conflicts of interest that threaten his investigation.

In Trump's latest tweets venting his frustration on Wednesday morning, he questioned why Sessions didn't fire acting FBI Director Andrew McCabe — who has been a target of Trump's dating back to his presidential campaign.

Trump is reportedly considering trying to replace Sessions using a recess appointment, according to The Washington Post.

Democrats have pledged to block any move by requiring the Senate to have pro-forma sessions throughout the August recess.

Graham added that if Trump wanted to fire Sessions he should use his authority to do so but should be ready to "accept the consequences."

Sessions, who served in the Senate for decades, is largely supported by his former GOP colleagues amid his escalating feud with the president.

Sen. Chuck Grassley Charles (Chuck) Ernest GrassleyGardner signals support for taking up Supreme Court nominee this year Grassley, Ernst pledge to 'evaluate' Trump's Supreme Court nominee McConnell digs in on vow to fill Ginsburg's Supreme Court seat MORE (R-Iowa), the chairman of the Judiciary Committee, warned on Wednesday night that his panel would not take up an attorney general nomination this year — a move that could effectively stonewall Trump if he fires Sessions.

Graham echoed Grassley's pledge, saying there would not be a confirmation hearing for another attorney general in 2017.