Here’s the real reason Trump and the GOP don’t want mail-in voting 

Trump and Republicans don’t want mail-in voting this November because it blows up a couple of their most effective voter suppression schemes.In presidential elections dating back to 2000, there’s been noticeable media coverage of long lines in majority-black precincts; commentators sometimes won

Source: Here’s the real reason Trump and the GOP don’t want mail-in voting – Alternet.org