Election workers in Milwaukee on Wednesday sort absentee ballots from Tuesday's primary election.

Richard L. Hasen, a professor of law and political science at the University of California at Irvine School of Law, is the author of “Election Meltdown: Dirty Tricks, Distrust, and the Threat to American Democracy.”

President Trump has recently come out against expanding voting by mail, despite the fact that he regularly votes by mail himself. He tweeted that it has “Tremendous potential for voter fraud and, for whatever reason, doesn’t work out well for Republicans.” Given that expanded mail-in voting is going to be an inevitable piece of the November election because of the coronavirus pandemic, it is important that Americans understand what risks come from voting by mail and what can be done about those risks before November, so that voters can have confidence that the election can be fairly conducted, in part, through mail-in balloting.