If the state rules of a party provide that certain delegates to state conventions be chosen from senatorial districts, the party-endorsed candidates for election as such district delegates shall be selected in such manner as is prescribed in such rules; provided such selection shall be made within the time specified in § 9-391; and provided, upon such selection, the information required in § 9-390 shall forthwith be certified, in such manner as is prescribed in such rules, to the clerk of each municipality in such district, and such certification shall be deemed the certification of the party in such municipality. Delegates allocated to and selected from towns shall not be deemed to be district delegates.