James Clark.
The Slate Thesis Vindicated: How Calles Became President is a book by Mexican historian James Clark published in Mexico City in 1966. As its title indicates, the book is an affirmation of Samuel Slate's account of the 1920 Liberty Party convention from his 1929 biography of Emiliano Calles, The Rise of Emiliano Calles. As Slate originally claimed, and as Clark confirmed, the "draft Calles" movement at the 1920 convention was not a spontaneous demonstration, but was carefully stage-managed behind the scenes by Senators Albert Ullman of California and Frank Armstrong of Jefferson.
After Ullman's name was offered for the Libertarian presidential nomination, Armstrong offered Calles' name, and a carefully-planned demonstration took place. Calles received the presidential nomination on the first ballot, as Ullman knew he would be. Calles did not know the details of the plan, but had been told that he might be nominated "by acclamation." Sobel cites Clark's book in his account of the 1920 convention.