The top Democrat on the Senate Intelligence Committee said Friday that it would be "uncharted territory" if President Donald Trump tried to fire the special counsel investigating Russian election meddling and possible collusion by the Trump campaign.
The statement comes a day after reports that Trump called for Mueller's firing in June.
"I think if the President had gone through with this, or tries to go through with it on a going forward basis, we're into uncharted territory," Sen. Mark Warner of Virginia told CNN's Jake Tapper on "The Lead" Friday. "We're into the real question of the fundamentals of our democracy."
Trump denied the reports, describing on Friday them as "fake news."
"These are not the actions of an individual who doesn't have something to hide," Warner said. "The President keeps saying, 'There's no there, there.' Well, if there's no there, there, let these investigations, including our bipartisan Senate intelligence investigation, finish our job."
On Thursday, reports surfaced that Trump had instructed the firing of special counsel Robert Mueller in June, just a month after Trump had fired FBI director James Comey. However, White House lawyer Don McGahn wouldn't give the directive to the Justice Department because he disagreed with Trump's reasoning, according to one person familiar with the matter.
The New York Times first reported that Trump had sought to fire Mueller, including that the President backed off after McGahn threatened to quit; a source told CNN that McGahn did not threaten to resign directly to the President.
When asked about findings in the Senate Intelligence Committee investigation, Warner said he has "reserved final judgment until we see all the witnesses and get all the facts."
"But we have seen enormously important documents, new documents, in the last 60 days, and you see particularly the President's supporters going out, making these outrageous, and at some level, silly charges with secret memos and secret societies being asserted," the Virginia Democrat said, referring to controversial text messages that were exchanged between officials at the FBI that some high-ranking Republicans allege is evidence of an anti-Trump bias among some who worked on the Russia probe.
There are currently several investigations into Russian meddling in the 2016 election in the House and Senate and by special counsel Robert Mueller.
Trump has repeatedly denied any collusion between his campaign and Russia.