Speculation that President Trump would consider firing special counsel Robert Mueller, who is investigating Russian meddling in the 2016 election, surfaced again Sunday and drew some fierce opposition from Republican lawmakers after two critical Twitter comments directed at the former FBI Director.

Trump has remained insistent that there was no collusion between his campaign and Russia and suggested the investigation is politically motivated. Trump on Saturday repeated the assertion that the investigation is a "witch hunt."

Trump's Twitter rants follow comments on Saturday from his lawyer, John Dowd, who "prayed" for an end to the investigation in the wake of the firing of former FBI Deputy Director Andrew McCabe.

"I pray that Acting Attorney General Rosenstein will follow the brilliant and courageous example of the FBI Office of Professional Responsibility and Attorney General Jeff Sessions and bring an end to alleged Russia collusion investigation manufactured by McCabe's boss James Comey based upon a fraudulent and corrupt dossier," Dowd told CNN in a statement.

On Sunday morning political shows, Republican lawmakers either dismissed suggestions that Trump would fire Mueller or offered a warning to the White House.

"I don't see the President firing him," Sen. James Lankford of Oklahoma said on ABC's "This Week."

"I think the White House has said 10 times, maybe more, that they're not going to fire Robert Mueller. They want him to be able to finish the investigation."

Sen. Rand Paul of Kentucky said he would not "advocate" for Trump to fire Mueller, while Sen. Lindsey Graham of South Carolina offered the sharpest rebuke.

"If he tried to do that, that would be the beginning of the end of his presidency," said Graham on CNN's "State of the Union."

Several Senate and House Republicans have been adamant that Mueller should proceed with the investigation. In December, Mother Jones reported on the many GOP lawmakers who have addressed the implications of firing Mueller.

“He is the best hope for giving us a product that the largest number of Americans can accept as credible,” Rep. Trey Gowdy of South Carolina, the chairman of the powerful House Oversight and Government Reform Committee, told the publication.

However, Republicans on the House Intelligence Committee on Monday closed their investigation of election meddling, claiming there was no evidence of collusion between Trump's campaign and Russia.

White House threats to fire Mueller are nothing new. The New York Times on Jan. 25 reported that Trump had ordered the firing of Mueller in June, but declined after White House counsel Donald McGahn threatened to quit over the matter.

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President Donald Trump arrives to speak to the media about his firing of Secretary of State Rex Tillerson before departing from the White House on March 13. Getty