A presidential historian said Sunday President Trump is "unfit for command" as chief executive.Rice University history professor and CNN analyst Douglas Brinkley said a week of White House personnel controversies proved the Trump administration was "in utter disarray.""And you can't really compartmentalize everything because it's all morphed together as Donald Trump's unfit for command, in my opinion," Brinkley said on CNN's "Reliable Sources."Brinkley doubled down when host Brian Stelter asked him to clarify his comment, saying Anthony Scaramucci's appointment as White House communications director was evidence of his point."I think when you have a White House communications director that uses the kind of foul language that he does against fellow employees of the federal government and makes threats the way that he did, and that's supposed to be your solution to the United States as a way they're going to communicate to the world, it means Donald Trump picked the wrong person to be his communications director," Brinkley said.Brinkley added Trump incorrectly thinks he can govern by chaos."We have a crisis in North Korea and we're playing these reality TV, big-time wrestling games because Donald Trump was weaned and raised on television," Brinkley said. "It's become like a TV episodic [presidency] where every day you've got to say something sensational to make sure your name's in the headlines."Brinkley also compared Trump's behavior with President Nixon's during the Watergate scandal, which ultimately result in Nixon's resignation."If you listen to the Nixon Watergate tapes, the secret tapes, and you hear Nixon ramble, it sounds like Donald Trump's tweets," Brinkley said. "And it didn't turn out well for Nixon."