Rosales faces long-time District Attorney Jaime Esparza.
Esparza has served for over 20 years as the district attorney and was once considered the heir-apparent to Congressman Silvestre Reyes. But several losses in high-profile cases and an election defeat of Reyes ended that.
Generally an elected official will endorse a candidate but not usually do much more than lend their name.
But this Facebook post indicates that the former mayor is obviously doing more than lending his name.