It is a known, documented fact that Russia has offered to do exactly that, wholesale electoral fraud. I'm not saying it happened in 2016, I'm saying it would be easier to get away with in 2020 than most people are giving credit for. You don't need to make 3 million votes appear or disappear to change an election, just tens of thousands in the right places. That's a much smaller trail to have to cover. It would be very naive to think that a foreign power couldn't alter the outcome of a closely contested election, especially if the sitting federal government turned a largely blind eye to their attempt. We shouldn't assume a fair election in 2020 as a given.