The Mayor of Kingston, New York, Shayne Gallo, is a Democrat, and he was defeated for re-nomination in the Democratic Party primary held on September 10. But he was also a candidate in the Green Party primary. Election officials will soon reveal whether he got enough write-ins in the Green Party primary to be on the November ballot as the Green nominee. See this story. UPDATE: the Green Party write-ins have now been tallied and Shayne Gallo lost the Green Party primary also. His Democratic opponent, Steve Noble, won the Green primary. See this story.
I doubt he would have campaigned as a Green.
Would a lawsuit from the GPNY be able to put an end to non-Greens winning their ballot line?
I don’t think the New York state law violates either the New York Constitution nor the U.S. Constitution. It is Green Party members who are deciding whether the Green Party should nominate certain candidates who are not members of the Green Party. In 1912 the New York State Court of Appeals (the highest state court in New York) said the New York Constitution protects the ability of two parties to jointly nominate the same person. New York statutes permit that. If the New York state Green Party passed a bylaw saying the party’s practice is to only nominate members, and then sued to enforce it, the state would probably respond that if the party doesn’t want to nominae non-members, it should just try to persuade its members not to nominate non-members.
As long as the New York state Green Party accepts the legitimacy of the law that says it should nominate by primary, then there really isn’t any logic for the party to say that, however, non-members should not be permitted to be write-in candidates in the party’s primary. This is an unfortunate consequence of the progressive era reform that forced parties to stop nominating by convention and start nominating by primary, whether they liked it or not.