investigating trump's campaign ties to russia, potential conflicts of interest, possible money laundering and other oversight matters that democrats say were ignored under gop control. that includes calling a number of people in trump's orbit to testify, potentially including trump organization cfo allen weisselberg who cohen mentioned multiple times in testimony in front of the house oversight committee. weisselberg signed one of cohen's reimbursement checks for paying alleged hush money ahead of the 2016 election. joining me now, ariana berg, former federal prosecutor with the southern district of new york. marc fisher, senior editor with the washington post. also coauthor of "trump revealed." mark, let me start with you. you know a lot about allen weisselberg and the role that he has played in sort of everything trump, right, the trump organization, the trump foundation. what is his role so far -- what has he been doing with authorities? he's had some limited immunity. and what can he help congress understand?