Former chief White House ethics lawyer Richard Painter told Chris Matthews that "the obstruction of justice and the lying" may be what brings down Donald Trump's presidency.

Painter, a law professor at the University of Minnesota, was a guest on MSNBC's "Hardball" to discuss Wednesday's bombshell report that special counsel Robert Mueller is requesting documents on Trump's actions since taking office.

"Richard, we know we like to talk about ethics with you, what do you make of the interest in the Trump Tower meeting and the decision that was made by team Trump about how the handle it, what to say to the media?" MSNBC host Stephanie Ruhle asked.

"Well, the problem is that meeting clearly was collaboration between the Trump campaign including the the Russians," Prof. Painter explained. "There was collaboration."

"After that meeting there was an effort to mischaracterize the meeting, to lie to the press about what was going on at the meeting, to say they're just talking about adoptions of Russian children," Prof. Painter explained.

"And apparently the President of the United States was involved in advising his son to tell lies to the press," Prof. Painter reminded. "Now, that's not in and of itself a crime, but the problem is that the subject matter of that meeting was under criminal investigation by Robert Mueller. So if the attempt is to get his son to tell a story that it is a lie to the press, and then lock himself into that lie...that would clearly be obstruction of justice."

"So what happened with respect to that meeting is critically important, as well as what happened with respect to firing James Comey, the FBI Director. If James Comey was fired because of the Russia investigation, in order to put a stop to it, which the president pretty much admitted in front of the Russian ambassador there in the Oval Office, if that's what really happened, I think there's a very strong case for obstruction of justice," Prof. Painter explained. "He has the power to fire the FBI director but not in order to obstruct an investigation of the collusion with Russia."

"Why is Mueller interested in President Trump's Oval Office meeting with the Russians?" Matthews asked. "Why would that meeting be of interest to the lawyers?"

"If he fired Director Comey in order to put a stop to the Russia investigation -- which is basically what he said in the Oval Office with the Russian ambassador -- if that's really why Director Comey was fired, in order obstruct the Russia investigation, that is obstruction of justice, pure and simple," Prof. Painter concluded.

"And there's obviously collaboration, they have to stop denying that," Prof. Painter noted. "The only question is whether it was illegal collaberation."

"The obstruction of justice and the lying may be what puts an end to this White House," Prof. Painter concluded. "They are in serious trouble on this"