Keller @ Large: Why Michael Flynn's Guilty Plea Is A Big Deal

BOSTON (CBS) - This is big. Really big.

Michael Flynn isn't George Papadopoulos, the relatively obscure Trump campaign aide who has also copped a guilty plea to lying to the feds about his Russian connections.

Flynn isn't Paul Manafort, the former Trump campaign manager, or his business crony Rick Gates, who've pleaded not guilty to a range of charges tied in part to their business dealings with "foreign agents."

Michael Flynn was one of Trump's closest political advisers, joining the campaign in February 2016, just a couple of months after his star turn dining next to Russian President Vladimir Putin at an event in Moscow. He led the chants of "lock her up" directed at Hillary Clinton from the stage of the Republican National Convention. And Flynn became the National Security Adviser last January before being forced out after he lied to White House officials and the FBI about his frequent discussions with the chief Russian envoy to Washington about sensitive policy issues.

The charges Flynn has acknowledged make him a convicted felon. But as CBS News notes, he could have had a much bigger book thrown at him. And in a statement Friday, Flynn says he's cooperating with Special Counsel Robert Mueller's probe of the Trump/Russia connection.

Keep in mind, it was Flynn who the president specifically singled out in his now-infamous conversation with then-FBI Director James Comey when he allegedly asked him to "let this go," an exchange that may be the crown jewel of any future obstruction of justice case against Trump.

Few individuals in the Trump inner circle have more potential to incriminate the president. If Flynn is turning on his former boss, look out below.

It was the release of incriminating audiotapes – the smoking gun - that led to President Richard Nixon's resignation in August 1974.

Michael Flynn could be Trump's smoking gun.