offering information on hillary clinton. they thought would help the trump campaign. >> reporter: manafort denied being involved with russia. also coming under scrutiny, michael flynn who trump ousted for failing to disclose his contacts with russia. >> we don't know who has been in charge. we don't know what they're being charged for. >> reporter: trey gowdy defending the probe as his republican colleagues call for a stop to the investigation. >> i will encourage my republican friends give a guy a chance to do his job. >> reporter: mueller's investigation ramping up in recent weeks. grilling reince priebus and former press secretary sean spicer earlier this month over the abrupt firing of fbi director james comey and closed door oval office meeting with russian foreign minister sergey lavrov. and also meeting with chris officer steele overseas. a former british spy whose now