Likewise, the results of the election should be plausible. If all votes go to one candidate, or the number of votes is vastly different than what was entered, people will get suspicious!
The trick here is that there are good statistical ways of measuring what "vastly different" means. In practice, it's only possible to swing the vote by 1-2% within the software as long as election officials are practicing even the smallest amount of due diligence. While that would have been enough to swing the last two US Presidential elections and some congressional elections, it won't work in the general case.
"There is no shame in being self-taught, only in not trying to learn in the first place." -- Atrus, Myst: The Book of D'ni.