During the Watergate investigations, a White House insider who refused to go on the record met with Woodward and/or Bernstein, usually in underground parking garages and other mysterious dark places. He was male (obvoiusly), well spoken, a heavy smoker (which I think disqualifies Mr. Ford but I can't be sure). He was also willing to bring down the Nixon administration due to what he perceived as malfeasance at the highest levels.
There's a short list of survivors who qualify on all counts. It will be interesting to find out the truth, perhaps this year.