The young Black mayor of Stockton, California, was a progressive superstar. Then a feisty local blog decided he had to go. — The plot against Michael Tubbs, the first Black mayor of Stockton, California, and the youngest person ever to run a major U.S. city, was conceived even before he took the oath of office, at the age of 26, on January 9, 2017. The mayorship was not a job for the…