I haven't seen an official number reported anywhere yet, but from looking at the machine vote totals we can guesstimate that about 21,000 Republicans and about 4300 Democrats voted by machine. With the 6100 or so paper ballots, it looks like about 31,400 people voted.

If this is the case, it appears Rikki's earlier prediction was just about spot on. It also means turnout was about 13%. Which to me is shockingly low given the circumstances of this election, but unfortunately seems to be par for the course in Knox County.