Yeah there are tons of loopholes in the voting system. Not just electronically...
In 2000 there were huge masses of a single party (some democrat faction) who went to the polls and stood in the booths for hours or something so other parties didn't have the chance to vote.
...there are still places where voting is done with scantron type ballots and people fill in bubbles with PENCIL instead of pen. Real secure there.
...and there's even been cases of people who work at the polls filling out the ballots of those who didn't show up to vote.
But the popular vote isn't what decides the race anyways, it's the electoral vote. So even if the popular vote is in favor of one candidate the electoral vote could change it all. So screwing with the popular voting system isn't necessarily going to decide the president.