You have to be registered to vote in TN period. I did one time a write-in vote for a candidate for a local office and I registered in Tennessee as Republican in 1979
No I mean the write in candidate has to be a legitimate, registered write in candidate.
I remember reading about it on the TN state site and it said something about having to be registered with TN to be a legitimate write in candidate. The deadline is something like 2 months before the primary or some such thing.