Reports suggest that voter fraud is very rare in the United States and mail-in ballots will not substantially increase the risk of voter fraud.
A study conducted by Stanford University’s Democracy & Polarization Lab concluded that neither party would benefit from an entirely mail-in-voting system, and it does not affect either party’s share of turnout, rather it increases the average turnout rates which contradict claims in the media and by some persons.
Further, Richard L. Hasen, a professor of law and political science has highlighted that problems are extremely rare in the five states that rely primarily on vote-by-mail. The number of fraud cases was few compared considering that there are millions of votes being cast in the general elections. The New York Times editorial has also noted that there is less chance of fraud in case of mail ballots, while an investigative journalism analysis on voter fraud identified only 491 cases of absentee ballot fraud from 2000 to 2012.
Therefore, the claim that mail-in voting 'substantially' increases the risk of fraud is false.