It's only a felony if it's fraud. If the laws in Ohio allow late changing in voter Party registration, or are a like Texas' law which doesn't require registration by party at all. The only restriction is that one is not allowed to vote in more than one party's primary, there is no fraud. There would only be fraud if folks were registered R and voted D, or perhaps is one is required to swear fealty to the party one is registering for, but that seems highly unlikely.
I can’t believe that a requirement to take a loyalty oath to a political party would hold up in court.