Democrats kept up the pressure on Donald Trump on Sunday over his firing of FBI director James Comey, as members of both parties said the president must turn over any secret recordings of the two men's conversations.
Trump tweeted on Friday that "James Comey better hope that there are no 'tapes' of our conversations before he starts leaking to the press!"
White House spokespeople later refused to say whether the president's conversations were in fact being secretly taped. 
But Democrats appearing on Sunday talk shows said the abrupt firing of the man leading an FBI inquiry into possible Russian meddling in the 2016 election and the Russia links of several Trump associates amounted to obstruction of justice. They called the president's tweet a clear attempt at intimidation.
If the current administration did make tapes, Senate Democratic leader Charles Schumer told CNN on Sunday, "the president should turn them over immediately, of course. To destroy them would be a violation of law."
In a separate appearance on NBC, he argued that it is important for the Justice Department to appoint a special prosecutor in the case because such a person would have "the ability to actually prosecute people for violations of law." 
Senator Mark Warner, the top Democrat on the intelligence committee, said that as his panel continues to investigate the Russia matter, it wants to "make sure those tapes, if they exist, are preserved."
'Tapes will be subpoenaed'  
Perhaps surprisingly, one of the most conservative Republicans in the Senate, Mike Lee of Utah, supported that call, telling a Fox News interviewer that it is "probably inevitable" that any tapes would have to be turned over.
"If, in fact, there are such recordings, I think those recordings will be subpoenaed and they will probably have to turn them over," said Lee, a member of the Judiciary Committee.
However, Lee gave Trump the benefit of the doubt, saying that "as far as I'm aware, he is fully cooperating and he is willing and eager to see this investigation" through.
Republican Senator Lindsey Graham said that the Judiciary Committee, of which he is also a member, needs Comey to appear before it to "clear the air."
"You can't be cute about tapes," he told NBC. "If there's tapes of this conversation, they need to be turned over." Trump's tweet, he added, was "inappropriate." 
Graham said he was "1,000 percent" sure that Russia had attempted to interfere with the election and he wanted Moscow to be "punished." But while he had no evidence of Russian collusion with the Trump team, "the president needs to back off and let the investigation go forward."
Institutions 'under assault'  
James Clapper, the director of national intelligence under former president Barack Obama, was asked on CNN whether he knew if Trump's White House was in fact secretly recording conversations.
"I can't say," he said.
But he expressed deep concern about the events swirling around the Russia inquiry.
"I think in many ways our institutions are under assault 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."
"Internally from the president?" he was asked.
"Exactly," Clapper replied, adding that the constitutional system of checks and balances was "under assault and is eroding."
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