My guess is that his resignation will occur only after he’s successfully scapegoated Don Jr. and the other one, claimed some kind of mental infirmity to avoid the bulk of the prosecution and signed another book deal.
As for actually beginning the process of voting - you draw this out as long as you can, let the wall of sound build, keep putting pressure on him and watch him implode.
This man is neither at the height of his physical or mental powers. Catastrophic failure is a matter of time and pressure.