[SmokingJoe]

There as massive ballot fraud in Detroit (Wayne County) in 2016. So much so that when Jill Stein demanded a recount in Michigan they found out that total votes cast far exceeded those registered to vote. Jill Stein was forced to withdraw her request for a recount in Michigan cause Trump would have ended up with a bigger winning margin. Trump still won in Michigan anyway despite all that fraud.
This year, Trump has put his own man in charge of the Post Office. Plus Homeland Security is hard at work putting in measures to thwart mail in fraud as we speak. Trump mentioned it in his interview with Hannity three weeks ago.

[Buckeye McFrog]

Homeland Security might be Trump’s best card here.

Issue a finding that foreign powers are planning to subvert the election with forged ballots and bar the practice of mail-in voting.

I presume that as CIC he would have extraordinary powers to do such a thing in the face of a clear threat.