Sen. Lindsey Graham Lindsey Olin GrahamMcConnell locks down key GOP votes in Supreme Court fight Will Republicans' rank hypocrisy hinder their rush to replace Ginsburg? Momentum growing among Republicans for Supreme Court vote before Election Day MORE (R-S.C.) said Tuesday that if President Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE fired special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE, it would "probably" be an impeachable offense.

Graham, a House prosecutor in the impeachment trial of former President Clinton, was asked if firing Mueller would be an impeachable offense during an interview on Hugh Hewitt's radio program.

"Probably so, if he did it without cause, yeah," Graham responded.

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"I think what the president will have done is stopped an investigation in whether or not his campaign colluded with the Russians, what effect the Russians had on the 2016 campaign. I can’t see it being anything other than a corrupt purpose," Graham explained.

Graham said that while he has seen no evidence of collusion between Trump associates and Russians, "to stop investigation without cause, I think, would be a constitutional crisis."

Graham's comments came after Trump attorney John Dowd called last week for Deputy Attorney General Rod Rosenstein Rod RosensteinDOJ kept investigators from completing probe of Trump ties to Russia: report Five takeaways from final Senate Intel Russia report FBI officials hid copies of Russia probe documents fearing Trump interference: book MORE to "bring an end" to Mueller's probe.

Dowd referenced the "courageous" action by 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 to fire FBI Deputy Director Andrew McCabe Andrew George McCabeGraham: Comey to testify about FBI's Russia probe, Mueller declined invitation Barr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' GOP votes to authorize subpoenas, depositions in Obama-era probe MORE over questions of bias.

Trump, Graham said, is not without reason for being upset with the Department of Justice over its surveillance of members of his 2016 campaign. But he said Mueller should be left alone.

"He would be wrong, in my view, to try to stop this investigation without cause on the Mueller side," he said.

Earlier this week, Graham pledged to make sure Mueller's investigation continues without any political interference, and warned that Trump firing the special counsel would herald "the beginning of the end of his presidency."

Trump reportedly ordered for the firing of Mueller earlier on in Mueller's investigation, but withdrew after top White House lawyers threatened to resign over the matter.

Graham’s remarks were markedly different from those of Sen. Angus King Angus KingShakespeare Theatre Company goes virtual for 'Will on the Hill...or Won't They?' On The Trail: How Nancy Pelosi could improbably become president Angus King: Ending election security briefings 'looks like a pre-cover-up' MORE (Vt.), an independent who caucuses with Democrats.

King said that it would be a “crisis” if Trump fired Mueller, but noted that he does not see it as an impeachable offense.

“High crimes and misdemeanors is the standard for impeachment, and I have a high standard for impeachment,” King told Hewitt. “I don’t think impeachment should be used to change a government you don’t like.”

“I wouldn’t say it rises to the level of an impeachable offense, but I certainly think it’s going to create a real problem,” he added.

Max Greenwood contributed

Updated at 12:14 p.m.