In the current state of affairs it has no application.
A constitutional crisis would be in an instance where a body of our government was attempting to act outside of the constitution.
With the checks and balances in place today it would be hard to reach that end.
As close as you come would be when Obama and his minions, most clearly Comey and Loretta Lynch were colluding behind the scenes to clear Hillary of her wrongdoing. using Lynch as the fall girl as it was by her imposing her power as AG to
be the final word after being coaxed or even threatened by her bosses.
The constitution clearly states in that case it would and should be up to the courts to decide her innocence or guilt, simply Lynchs job to recommend the courts look into it based on her recommendation to do so by Comey.
Which he didn't, based on nothing any lawyer worth his weight would have decided given the evidence as presented.