If you agree there shouldn't be campaigning in the election thread, you should agree with the invalidation of the ballot. Open and shut.
In reality, you *don't* agree with the campaigning ban.
Non sequitor.
Pretty much every jurisdiction has a ban on campaigning in the ballot box. Arguing a hypothetical does nothing to address the point. As you said, you agree with the ban on campaigning. The ban is in place for a good reason. That thread needs to be kept clean so as to make counting easier.
Pretty much every jurisdiction has laws regulating the format that ballots must follow, and there's a whole series of regulations - including invalidation for altering your ballot, etc.
Are you suggesting those regulations are also unconstitutional? Or do you not care about those because they won't help labor this election?