From The Washington Post :
A recent open letter  sent to congressional leaders underscores these points. The document, signed by Stan Veuger of the conservative American Enterprise Institute, Eli Lehrer of the libertarian R Street Institute, a batch of former Republican congressmen and Michael Steele, former head of the RNC, seeks additional funding for state vote-by-mail operations. It explains that “voting by mail has already been used by tens of millions of Americans, as well as members of the military, for decades and does not favor either political party.” They explained that in 2016, “nearly a quarter of all voters in the 2016 cast their ballots by mail.” They pointed to opinion polling showing more than 70 percent of voters and nearly two-thirds of Republicans want to guarantee voting by mail.
- “The Washington Post”: https://www.washingtonpost.com/opinions/2020/08/05/trump-lets-that-his-voting-by-mail-attack-is-fake/?outputType=amp&usqp=mq331AQFKAGwASA%3D&_js_v=0.1
- “open letter”: https://www.aei.org/articles/coalition-letter-in-support-of-vote-by-mail/