San Antonio voted for Obama in 2008 and 2012. Hillary Clinton in 2016, and Biden in 2020. It trends to the left, but is not the lefty mecca that Austin is. Its current mayor is an Independent.
Per city charter, all mayors run as independent. Make no mistake, though, Ron Niremburg is a major lefty. He won in 2017 over Ivy Taylor (black, female, and also Democrat) after she asked about how a proposed gay rights bill would affect religious liberty. Mayor Taylor also had the audacity to defeat Leticia Van de Putte in her first election, so she was already unpopular with the local lefty media.