I think it will be pretty hard to ‘rig’ an election of the sort we will have this year.
(They tried last time, spent millions upon millions, with all the propaganda that a friendly, colluding MSM could provide - and STILL failed miserably.)
The lesson the rats learned in 18 was in 16 they didn’t cheat enough. Trump will need a lot of cushion to beat it. It looks pretty good right now but I wish they had gone after the cheating a lot more.