The members of the national party executive committee of any political party, to which the state is entitled under the national organization and the rules and regulations of the national committee of the party, shall be elected by the state executive committee of such party, unless the rules of the national party otherwise provide, in which latter event they shall be selected in all respects as provided for the selection thereof by the rules and regulations of the national organization of the political party and the resolutions of the delegated representatives of the political party passed and adopted by any national convention of such political party. A vacancy in the membership of a national party executive committee shall be filled by the state committee of the party unless the rules of the national party otherwise provide.