It is not election fraud when there isn't an election. Nominations in a party are just that - nominations. And, in the case of caucuses there are nominated delegates that aren't registered as candidates with anyone.
There would be no authority for a sheriff to do anything about events at a private meeting.
The best we can hope for is a story being picked up on the Daily Show - I'm serious about that.
"In the beginning of a change the patriot is a scarce man, and brave, and hated and scorned. When his cause succeeds, the timid join him, for then it costs nothing to be a patriot."--Mark Twain