Let’s see who signed the checks.
And work backwards from there.
Seriously? You expect they wrote things down in a traceable manner?
Nah, you'll have to start by looking for surveillance video of attache cases filled with $100 bills being passed from car trunk to car trunk at night in an alley.
Treasurers bear a lot of legal responsibility. The seldom-mentioned Andrew Tobias was the DNC Treasurer for years and years - until this year.