After eight years, four elections, hundreds of protests, and a pandemic, Ron Nirenberg walked out of San Antonio’s city hall as mayor for the last time on June 18. Once referred to as “Liberal Ron,” the 48-year-old had more recently served as a pragmatic counterbalance to the city council, which has shifted from the pro-business orientation of Julián Castro’s “Decade of Downtown” to a more activist and progressive body pushing opposition to state and national politics. For the immediate future, Nirenberg will teach communication at his local alma mater, Trinity University, probably sticking to his regimen of weight lifting, taco eating, and Spurs watching. But he admits that he’s not done with politics or public service—though the former is generally what he has to put…