Sen. Susan Collins R-Maine, warned Sunday that President Trump shouldn’t fire the deputy attorney general of the Justice Department in order get to special counsel Robert Mueller.

Last summer, Trump reportedly wanted to fire Mueller, who is investigating Russian interference in the 2016 election and possibly obstruction of justice by the president.

“The president had a bad idea, he talked to his counsel who explained to president why it was a bad idea,” Collins said of reports that White House counsel Don McGahn threatened to quit if Trump tried to fire Mueller.

In an interview on CNN's "State of the Union," Collins stressed that the president cannot technically fire Mueller, but the deputy attorney general, Rod Rosenstein, can. Rosenstein told Collins he wouldn’t give in to White House pressure to fire Mueller.

Pressed on more reports that Trump has considered firing Rosenstein as well, Collins said that wouldn’t end well for the president.

“If that’s true, that obviously would be a terrible mistake,” she said, pointing to former President Nixon’s infamous firing spree during Watergate.

“The president would be best served by never discussing the investigation, ever,” Collins said.

"It probably wouldn’t hurt for us to pass one of those bills," Collins said. "It wouldn’t hurt to put that extra safeguard in case, given the latest stories."