If in any legislative district, the number of persons nominated by nominating petitions exceeds four to be elected delegates to the constitutional convention from such district, then a nonpartisan primary shall be held in such district on the third Tuesday after the first Monday in September before the special election for such candidates. At such primary the four persons receiving the greatest number of votes shall be chosen from those nominated by nominating petitions. Those so chosen shall be deemed nominated for delegates, and their names only shall appear on the ballot at the special election. At such primary election each elector shall be entitled to vote for two candidates. No party or political designation shall appear on the ballots, either at the primary or special election provided for by sections 49-212 to 49-234.