You had better believe he could.
Yes, yes: I know. The law. The US Constitution.
Wake up. Those have already been demonstrated to be mostly irrelevant.
Trump has spent billions on a border wall despite not having the authorization
from Congress, and has gotten away with it.
He has refused to allow Congress its power to subpoena witnesses, and he has
gotten away with it.
He has received foreign emoluments, and he has gotten away with it.
Assertions that the election must happen on time, as scheduled, just because
some dusty old pieces of paper have words saying they must are Establishment
types whistling past the graveyard. The old order has already died, and they have yet to realize it.
He’s already deploying goons to the major cities. They could easily intimidate people into staying home on Election Day, or even be dispatched to polling stations to disrupt them. Many states are controlled by Trumpists, and would gladly obey their fuhrer’s orders to not hold the elections if so requested.
The rule of law can’t save freedom. Only mass pressure from below can.