defying the president's red line, cnn has learned special counsel bob mueller is now looking into the president's finances as he investigates possible collusion with russians during this election, and two republican senators, i hear, first susan collins, she is championing the investigation's expansion in this exclusive interview with dana bash. she says mueller should explore whatever avenues necessary. >> i believe that the special counsel has a very broad mandate, and he should follow the leads wherever they may be. and thus, i do not think his investigation should be constrained beyond the mandate that he was given when he was subpoenaed. >> and the president called that a red line.