colonel vindman, obviously is going to be at the top of their list. fiona hill, former top russia advisor on the national security council is also going to be high on that list. anybody who can essentially speak to the public to back up the allegations of a quid pro quo. the first part of that being the idea that the white house meeting between president trump and president zelensky was used as leverage to get these politically-motivated investigations that the president wanted. the second aspect of that being, of course, the military aid to ukraine. democrats feel like they have less evidence of that and more evidence that the meeting was leveraged as part of the quid pro quo. and the military aid remains a glaring blindspot for them. i've talked to democrats who say that basically the reason why they haven't figured out why the aid was initially put on hold and sort of what the internal machination of that were is because these officials from the office of management and budget just have not shown up. out of all of these sort of executive branch departments and agencies who have been asked to