Victor asked:
"Sincere question: What do you think the grounds against sore loser laws Constitutionality would be?"
Quite simply:
Violation of the First Amendment's guarantee to exercise one's right of free speech.
Look back to only a few years ago, to the "Citizen's United" case that overturned laws against limits on campaign spending by political organizations -- again on the grounds that to place arbitrary limits on such spending restrained the right of such organizations to express themselves politically as guaranteed by the Constitution.
Then consider this:
What greater "right" to free speech and political expression can there be, than to run for public office based on one's beliefs?
I predict the foundation of Blankenship's case against the state "sore loser" law is that it prohibits a citizen's right to political expression by denying them the opportunity to exercise it by running for office -- regardless of any "prior runs" as the candidate for the nomination of one party or another.
And... that any attempt to limit such right by putting into place a barrier (the "sore loser law") is an arbitrary and unreasonable Constitutional violation of such "expression".
This might even be found to violate the 14th Amendement's guarantee of "equal protection under the law", in that Blankenship was denied the opportunity to run whereas someone who had not previously run (in any party's primary) would NOT be so denied.
And in finding so, the Supreme Court will declare West Virginia's sore loser law unconstitutional, and in so doing, so will all other similar laws at all levels of government be declared same.
That's how I see it.
I could be wrong.
But if Blankenship promulgates this complaint, that's how I expect things to go.