He knows he's gonna get mullered in the Mid-terms so he's playing out a multi-pronged approach to try and prevent this.
1) Sowing seeds of doubt and alleged interference in the election even before they take place so he can declare them illegitimate/declare a national emergency.
2) Attempting to bribe voters.
3) Supreme Court agreeing that he can restrict postal votes.
4) Voter interference - already hinting that he'll send in the National Guard to Decmocrat/swing states around polling day.
I actually think that his base would vote for him, even if he literally shot them in the face first.
However, I'm holding onto some vain hope that Americans aren't as f***ing stupid as they look at the moment and stop this happening.