(CNN) Even as President Trump was on Twitter insisting that the indictment of former campaign chairman Paul Manafort was meaningless because it involved activities unrelated to Trump or the campaign came news that former Trump foreign policy adviser George Papadopoulos had pled guilty to lying to the FBI about his contacts with, wait for it, Russia.

The Manafort news drew the bigger headlines Monday morning -- understandable given his high-profile role at the top of the Trump campaign. But, the Papadopoulos guilty plea -- and the fact that he has been cooperating with the special counsel investigation since his July arrest -- strikes me as significantly more problematic for Trump and his White House in the medium-to-long term.

"In truth and in fact, however, and as set forth above, defendant PAPADOPOULOS met the Professor for the first time on or about March 14, 2016, after defendant PAPADOPOULOS had already learned he would be a foreign policy advisor for the Campaign; the Professor showed interest in defendant PAPADOPOULOS only after learning of his role on the Campaign; and the Professor told defendant PAPADOPOULOS about the Russians possessing" dirt" on then-candidate Clinton in late April 2016, more than a month after defendant PAPADOPOULOS had joined the Campaign."

So, Papadopoulos copped to lying to the FBI about the timing of his contacts with Russians. In his initial interview in January 2017, Papadopoulos was insistent that he had reached out to his foreign contact "The Professor" (amazing!) before he had formally joined the Trump presidential campaign. He was arrested in July, pleaded guilty in October and appears to have been cooperating in between.

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