As far as voter fraud as it is commonly considered: Yes, there are cases on record, but it's much rarer now than it used to be.
One obvious reason is that we have computers now, as you may have noticed.
Another reason is that, simply, it's not worth it for a national election. The amount of effort it takes to fraudulently cast a single vote is immense when you compare it with the return, and to get millions is just about impossible. Far easier and more effective to suppress the votes you DON'T want, and lie to the public to get them to change the way they vote. You know, like Trump is doing.