investigationing a campaign i have a role in. >> reporter: the well of affection runs deep. sessions was the first senator to endorse the long-shot presidential candidate in february, 2016. >> i am pleased to endorse donald trump for the presidency of the united states. >> reporter: at a time when many in the gop eye trump, sessions became one of trump's biggest boosters on the campaign trail. >> there's one man with a strength, a courage, determination, the guts, the challenge, the thing that is are going wrong in this country and put us on the right track. that's donald j. trump. >> reporter: a close adviser, even flying to indiana to huddle with trump as he wrestled with who to choose as his running mate. trump repaying that loyalty soon after he won the election naming sessions to serve as attorney general. >> jeff understands the job of