Transcript for Paul Manafort agrees to cooperate with special counsel

developing stories this Friday ING. Ul manafor flipping, and now cooperating with Robert Mueller. Entering into de pleading guilty to avd upcoming trial. Court documents and all matters.here's piee Thomas. Reporter: He was the picture of cdence, theampaign chairman at Donald trun national convenon. But Y in courtpaul manafort appeared N, softly ding guilty to multiple feni at times his voice barel A tough day for Mr. Manafort. He has accepted responsibility. Rter: He waalready onk an tax frau he has now agreed to cooperate with special counsel Robert Mueller. He's agreeing to cooperate, do you expect that hel do so lly and thoughly? We do. Fully and truly. Prosecutors debe a broad coopreement covering "Any andll matters" the government deems relevant. That will likew-infamousrump tower., red kushneand manafo sitting wn with a Kremlin connecd attorney they told had dihillary. Nafort is E fourth tmp campaign official to plead guilty in recent months. Just wpresident's formersorning on tmp. This whole thing about flipping, they call it. Itost ought to be outlawed. It's not . Pierre joins us live from shgton. W is the president's team responding to news that manais now cooperating with the specialcounse Rter: We have Stant from R ul once again itigation H conclude pleaaving nothg with the

This transcript has been automatically generated and may not be 100% accurate.