On September 2, 2020, Trump told supporters in North Carolina that they should vote by mail, and then vote in person to ensure it counts. Because double voting in such a manner is felony fraud, the North Carolina Board of Elections issued a statement urging people not to follow Trump’s advice. Trump has alleged widespread fraud since the 2016 election, though an investigative commission found none.

…send it in early and then go and vote and if it’s not tabulated, you vote and the vote is going to count. You can’t let them take your vote away. These people are playing dirty politics, dirty politics.

So if you have an absentee ballot, or as I call it a solicited ballot, you send it in, but I would check it in any event. I would go and follow it and go vote.

When Trump repeated his suggestion via Twitter, the company flagged the tweet with a special notice:

In an interview with CNN’s Wolf Blitzer, Trump’s Attorney General William Barr evaded questions on the issue by claiming that he didn’t know state voting laws well enough to comment.

Trump also once registered to vote in Florida despite claiming DC as his legal address.

The New York Times – Trump Encourages People in North Carolina to Vote Twice, Which Is Illegal
NPR – Trump Urges Supporters To Go To Polls Even After Voting By Mail
North Carolina Board of Elections – A Message from Karen Brinson Bell to NC Voters
CNN – Ignoring warnings from election officials, Trump again suggests supporters should try to vote twice