Who is the plaintiff?
Cruz would be the plaintiff, seeking a declaration of his eligible status. The question would be, who is the defendant? I suppose the answer could be a state official in charge of elections, but there would to be a real "case or controversy," so Cruz could really only file such an action if there was some reason to believe that the official would likely bar Cruz from the ballot.
Methinks Trump should stick to his area of expertise, and stop handing out "free legal advice" (e.g., engaging in the unauthorized practice of law)
Grayson a US Rep is going to sue and he will have standing.
I’m not sure why Trump is getting flak for raising a real issue.