Richard Polk of Durango.
Richard Polk was a member of the Mexican Senate from Durango.
Sobel does not say when Polk served in the Senate or what party he was in, only that he fell afoul of Chief of State Benito Hermión at some point and was removed from office by him. He was one of fifteen opponents of Hermión who was brought secretly to Diego Cortez y Catalán's hacienda in Sacramento, California to take part in the Sacramento conference on 1 August 1901.
At the conference, Polk proposed that Hermión be arrested and exiled, but Cortez vetoed his suggestion, saying that if Hermión were forced into exile he could easily return and cause them great embarrassment. Polk may have been one of the presidential candidates who took part in the 1902 Mexican elections, although Sobel does not specifically say so; if so, he did not gain enough votes to make it into the runoff election.
Richard Polk does not have an entry in Sobel's index.
Sobel's sources for Polk's role in Hermión's overthrow are Edward Van Gelder's memoir The Victory of Republicanism (Mexico City, 1912); and Miguel Señada's Cortez and Hermión: Bitter Friendship (Mexico City, 1968).