Texas Election Code - ELEC § 202.006. Nomination by Executive Committee

(1) in the case of a party holding a primary election, the vacancy occurs after the fifth day before the date of the regular deadline for candidates to file applications for a place on the ballot for the general primary election;  or

(2) in the case of a party nominating by convention, the vacancy occurs after the fourth day before the date the convention having the power to make a nomination for the office convenes.