Conceivably, Trump issues a pardon to himself publicly as a catalyst for Dems to sue.
If the Supreme Court overturns it, then it would also potentially overturn thousands of (over classified) top secret pardons by Obama , Clinton and both Bushes.
Including prior pardons of themselves.
https://mobile.twitter.com/ScottAdamsSays/status/1331589403265835009
And then Trump retains his office anyway and is then free to hold prior presidents accountable for their crimes.