Not sure ‘Doc’ considered himself a Republican. He was a Georgia boy by way of Texas. The Earps were for sure. Northerners, Jim & Virgil fighting for the North in the Civil War. The dad fighting in the Blackhawk War. Doc affiliated with them because of his friendship with Wyatt Earp. And Doc wasn’t a cattle thief as were the opposition. Yep, the problems in Tombstone pretty much split among party lines back then (as today), even down to the two newspapers.
When you get down and dig, I find it weird how things back then were the same as they are today. Especially here in Arizona.