Trump has no power to “decree” that voters must present ID or to end mail-in balloting. But that doesn’t mean he can’t at least try both. Under the Insurrection Act or some other dusty statute, he can declare a state of emergency. Then he can decide that said state permits, nay requires, him to take extraordinary measures. On October 5, say, that might mean outlawing early voting. By October 13, it might mean no mail-in voting. By October 29, a reminder that all voters must present ID to vote. And by Sunday, November 1, two days before the election—an announcement that all these “reasonable” measures have alas failed, and he is now forced, against his will, to postpone the election.
You already lost mail in voting without even realizing. The Supreme Court said post office doesn’t legally have to deliver mail and can’t be sued for it. Do you really think any mail in ballots will be delivered?, when they already changed it so anything delivered after the date doesn’t count? You’ve already lost and don’t even realize it.