May 14 (UPI) -- U.S. government institutions are "under assault," former Director of National Intelligence James Clapper said Sunday -- reacting to President Donald Trump's recent firing of FBI Director James Comey.
Comey was leading the federal agency's investigation of Russian interference in the U.S. presidential election and possible collusion with Trump's campaign staff.
"I think in many ways our institutions are under assault both externally -- and that's the big news here is the Russian interference in our election system -- and I think as well our institutions are under assault internally," Clapper said on CNN's State of the Union.
Anchor Jake Tapper asked Clapper if the institutions were attacked internally by Trump. Clapper responded, "Exactly."
Clapper said the legislative and judicial branches can thwart abuse of power by the executive branch.
"The founding fathers, in their genius, created a system of three co-equal branches of government and a built-in system of checks and balances," Clapper said. "I feel as though that is under assault and is eroding."
Congressional Democrats and several Republicans want the Department of Justice to appoint a special prosecutor or to establish an independent investigative body.
Utah Republican Sen. Mike Lee said on Fox News Sunday that Trump should appoint Court of Appeal Judge Merrick Garland to head the FBI. Garland was President Barack Obama's pick to replace Supreme Court Justice Antonin Scalia after Scalia's death last year but the Republicans refused to consider him for the vacancy. Then, Trump nominated Neil Gorsuch, who was confirmed.
"One name that I think the White House really ought to consider is Merrick Garland," Lee said. "I think this would be an exciting pick.
Josh Holmes, a former aide to Senate Majority Leader Mitch McConnell, said the Republican leader had just called him to say he would support Garland for FBI's top spot.
On Sunday, Senate Minority Leader Chuck Schumer said he would support an effort to block any nominee to lead the FBI until an independent prosecutor is named.
"We'll have to discuss it as a caucus, but I would support that move," Schumer said on CNN's State of the Union.
Schumer said independence is vital.
"To have that special prosecutor, people would breathe a sigh of relief, because then there would be a real independent person overlooking the FBI director," the New York Democrat said. "The key here, of course, is getting some of our Republican colleagues to join us. We're hoping. We're waiting. We understand it's difficult, but I think patriotism and the needs of this country demand it."
Virginia Democratic Sen. Mark Warner said the firing appears as an attempt to squash the agency's investigation.
"The president's actions and his statement lends to that appearance," Warner, the top Democrat on the Senate intelligence committee, told Fox News Sunday.
In an interview broadcast Saturday on Fox News' Justice with Judge Jeanine, Trump said he decided to fire Comey because he could no longer trust him.
Trump has determined from Clapper's previous Senate testimony that there was no "no evidence" of collusion.
But Clapper said that is not true.
"The bottom line is I don't know if there was collusion, political collusion," Clapper told Tapper. "I don't know of any evidence to it. So I can't refute it, and I can't confirm it."
Secretary of State Rex Tillerson said Russia's attempts to interfere with the 2016 election did not come up during in-person meetings and conversations among the White House, State Department, and Russian Foreign Minister Sergei Lavrov last Wednesday.
"I think we have such a broad range of important issues that have to be addressed in the U.S.-Russia relationship," TIllerson said during an interview on NBC's Meet The Press that aired Sunday. "Obviously the interference in the election is one of those. I think it's been well documented, it's pretty well understood, the nature of that interference, here and elsewhere."
Sen. Lindsey Graham, R-S.C., said it was "absolute not" possible for the United States to further a relationship with Russia until election meddling has been addressed.
"Russia didn't change the outcome of the election, but they sure as hell tried," Graham said on Meet the Press. "And I want to punish the Russians. And I hope the president will see their interference as a threat to our democracy."
In an NBC/Wall Street Journal poll, 65 percent say they have a "great deal" of confidence or "some" confidence in the FBI's ability to conduct a fair and impartial investigation into Russia's involvement in the 2016 election. A combined 40 percent who say the same of Congress.
And asked if they prefer Congress or an independent commission or special prosecutor to investigate Russia's involvement, just 15 percent pick Congress, while 78 percent support an independent commission or special prosecutor.
The NBC/WSJ poll was conducted Thursday through Sunday of 800 adults with a margin of error of 3.5 percentage points.