Fazio's article is an interesting portrait of Marcus A. Smith, but it doesn't provide much detail about the Earp- Clanton troubles. It may be of interest that he and Lyttleton Price, the district attorney, became partners in a mine in Tombstone in December, 1881. He was a Democrat, and he was one of the leaders of the "indignation meeting" which met to protest President Chester Arthur's threat to declare martial law in Arizona in 1882. He gave a rousing speech in which he denied that outlawry was rampant in Cochise County. This helped to get him elected District Attorney in the election of 1882.
There is a Marcus Aurelius Smith Collection at the Arizona Historical Society, but it is mostly concerned with his later career in national politics. Fazio does not cite any Smith recollection relating to the Earp-Clanton conflict. Fazio's article (A&W, Spring 1970)was based upon his Master's thesis, completed in 1968 at the University of Arizona.