It's not illegal unless votes are cast from both... it's not even uncommon.
No chit sherlock, and the same does not equal five million fraudulent voters going into a poll and voting twice or using a fake ID. You supported this guy and you deny the same, and now you argue that registration problems do not equal fraud, yet you refuse to recognize that the popular vote was not fraudulent voters and in fact it was relevant and not one of your get over it comrade moments. The solution is simple. When a person is registered to vote, you take a photo, and all the traditional information which is downloaded on secure servers in the county of registration. A voter comes to vote, he does not have to produce an ID, and when they check a person in they simply go to the database photo and hand the person a ballot. In the event the person does not look exactly the same, the person still votes, but the folks at the voting precinct by statute take a photo of the individual claiming to be the registrant, and they turn those over to the county SA who investigates every variance in that county. Zero voter fraud, or prosecution, and most important no voter suppression on election day. Done.