Is there a coming constitutional crisis?

Keith Whittington thinks there would be a crisis if Trump fires Mueller and then the Republicans in Congress refuse to hold Trump to “account,” which I assume means impeachment or something like it. I don’t see it. If Trump fires Mueller, and Congress doesn’t impeach Trump, then the outcome might be unfortunate but it is not a crisis since government would continue to operate as it always has. A crisis requires more than a constitutional violation (if that is what the firing of Mueller would be, but that is hardly clear). It requires an impasse of the sort that would arise when government officials receive conflicting orders from different sources claiming constitutional authority and are unable to resolve these conflicts in a consistent and predictable way, based on legal materials.

Such an outcome is certainly imaginable, but is it likely? If Trump fires Mueller, Mueller will step down. He won’t claim that the firing is null and void. Nor will anyone else. It is remotely possible that Congress would impeach Trump but I doubt it, and even then, there is no crisis unless Trump is actually convicted and then refuses to leave office.

We can imagine a more plausible path to a constitutional crisis, one that does not depend on the Republicans in Congress to abandon their political interests. Let’s map it out, with (conditional) probabilities.

1. Trump is found to have obstructed justice or committed some other serious crime (p = 0.5).

2. Special counsel Mueller brings charges against Trump in violation of apparent Justice Department policy (p = 0.2).

3. A court agrees to hold a trial rather than issue continuances until Trump leaves office (p = 0.3).

4. Trump is found guilty by a jury (p = 0.5).

5. Trump is sentenced to jail rather than required to pay a fine (p = 0.1).

6. Trump loses on his various emergency appeals (p = 0.5).

7. Trump refuses to report to jail and orders the Secret Service to turn away federal marshals who come to arrest him (p = 0.9).

8. The Secret Service obeys Trump rather than their boss, the Secretary of the Department of Homeland Security (p = 0.1).

I say at this point a genuine constitutional crisis has begun. But p = 0.000675. Does anyone think my probability estimates are too low, enough to make a difference? Or that there is a shorter path to crisis?