Washington (CNN) The No. 2 Democrat in the Senate says Republicans may be setting the stage for a "constitutional crisis" if they use the Nunes memo to end the special counsel's Russia investigation.

"To say that that's the end of the investigation, that this is all that Donald Trump needs to fire (Deputy Attorney General Rod) Rosenstein or to fire (special counsel Robert) Mueller, I'll just tell you, this could precipitate a constitutional crisis," Sen. Dick Durbin, D-Illinois, said on CNN's "State of the Union" on Sunday.

The four-page memo alleges FBI abuses of the Foreign Intelligence Surveillance Act, accusing the agency of improperly using information paid for in part by Hillary Clinton's campaign to obtain a FISA warrant for Trump campaign foreign policy adviser Carter Page. Trump has said the memo " totally vindicates " him in the Russia probe.

"If House Republicans believe that they've set the stage for this President to end this investigation, they are basically saying that in America, one man is above the law, and that's not a fact," Durbin added.

California Rep. Adam Schiff, the top Democrat on the House Intelligence Committee, argued in an Esquire op-ed that Trump is seeking to seize the FBI for political ends.

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