Belmares is the former co-chair of the Community Alliance for a United San Antonio (CAUSA), the coalition that worked to get the 2013 non-discrimination ordinance passed.
When County Judge Nelson Wolff announced his retirement last year, Sakai, 67, stepped down from his district court bench to make his dedication to the race clear to voters.
The El Paso native is locked in a May 24 runoff with former district court Judge Peter Sakai to represent the Democratic Party in the high-stakes race.