Texas Local Government Code - LOC GOV'T § 25.022. Petition

(a) The residents of the municipality may file a petition with the clerk of the municipality requesting the mayor to call a special election to determine whether the municipality shall adopt the city manager form of government.

(b) The petition must be signed by a number of qualified voters equal to at least 20 percent of the total number of qualified voters who voted for mayor at the most recent municipal election at which the office of mayor was to be filled.