Texas Election Code - ELEC § 174.096. Voting at Convention

(1) the delegates selected by a particular county or senatorial district convention who attend the biennial state convention are entitled to cast a number of votes equal to as many delegates as that county or senatorial district convention was entitled to select;

(2) a person may not vote a proxy for delegates from more than one county or senatorial district;  and

(3) a person who votes a proxy for a delegate from a county may not do so for a delegate from a senatorial district and vice versa.