From the May 16 edition of CNN's Anderson Cooper 360:
DAVID GERGEN: I must say, I was in the Nixon administration as you know, and I thought I'd -- after watching the Clinton impeachment, I thought I would never see another one. But I think we're in impeachment territory for the first time.
ANDERSON COOPER (HOST): Really?
GERGEN: Well, I think that the obstruction of justice was the number one charge against Nixon that brought him down. Obstruction of justice was the number one charge against Bill Clinton, which led to his indictment in the house, and he won in the Senate.
And I think -- I'm a lapsed lawyer, I can not tell you if it meets all of the legal definitions, but I can tell you from a lay point of view, it looks like he was trying to impede the investigation, he was using his power to do that, and when James Comey didn't go along with him, he wasn't his boy, he fired him, which I think is also relevant to the question of what he was trying to do.
So, from my point of view, this is of enormous consequence for his presidency. I think if you look at the three bombshells that we have had, the Comey firing last week, then the sharing of this highly classified information with the Russians of all people, and now telling Comey to drop the case, what we see is a presidency that's starting to come apart.