On April 23, Mark Fisher won a procedural ruling in his lawsuit against the Massachusetts Republican Party. There will be a trial on June 18. The party had tried to get the case dismissed without the need for a trial.
Massachusetts Republican Party rules say a candidate needs 15% support at the state convention, or he or she cannot petition for a place on the primary ballot. Nothing in state law authorizes the 15% rule, but both federal and state courts in Massachusetts have ruled that if parties want to place additional hurdles to their own primary ballot, they may do so.
The lawsuit involves a dispute as to whether Fisher got 15% support at the March Republican state convention. He does have 15.15% if blank ballots are not included, but only 14.785% if they are included. Roberts Rules of Order say blank ballots should not be counted, and the party rules say that Roberts Rules of Order should apply. See this story for more details. It seems conceivable that the party might wish to give in before the trial starts. Even if Fisher wins the lawsuit, he still needs 10,000 signatures of registered Republicans and/or registered independents. Presumably he is already working on that petition, because the signatures are due May 6.