WASHINGTON, Aug 25 (Reuters) - U.S. President Donald Trump on Friday granted a pardon to former Arizona lawman and political ally Joe Arpaio, the self-proclaimed "toughest sheriff in America," less than a month after he was convicted of criminal contempt in a case involving his department's racial profiling policy.Trump had signaled this week that the first presidential pardon of his administration would go to Arpaio, 85, whom he has frequently praised for his hardline immigration stance. (Reporting by Julia Harte; Editing by Sandra Maler)