At the general election on the first Tuesday following the first Monday in November 1962, and every twenty years thereafter, the secretary of state shall, and at any general or special election the general assembly by law may, submit to the electors of the state the question “Shall there be a convention to revise and amend the constitution?” The question shall be submitted on a separate ballot without party designation, and if a majority of the votes cast thereon is for the affirmative, the governor shall call an election of delegates to the convention on a day not less than three nor more than six months after the election on the question. At the election the electors of the state shall elect fifteen delegates-at-large and the electors of each state senatorial district shall elect two delegates. Each delegate shall possess the qualifications of a senator; and no person holding any other office of trust or profit (officers of the organized militia, school directors, justices of the peace and notaries public excepted) shall be eligible to be elected a delegate. To secure representation from different political parties in each senatorial district, in the manner prescribed by its senatorial district committee each political party shall nominate but one candidate for delegate from each senatorial district, the certificate of nomination shall be filed in the office of the secretary of state at least thirty days before the election, each candidate shall be voted for on a separate ballot bearing the party designation, each elector shall vote for but one of the candidates, and the two candidates receiving the highest number of votes in each senatorial district shall be elected. Candidates for delegates-at-large shall be nominated by nominating petitions only, which shall be signed by electors of the state equal to five percent of the legal voters in the senatorial district in which the candidate resides until otherwise provided by law, and shall be verified as provided by law for initiative petitions, and filed in the office of the secretary of state at least thirty days before the election. All such candidates shall be voted for on a separate ballot without party designation, and the fifteen receiving the highest number of votes shall be elected. Not less than fifteen days before the election, the secretary of state shall certify to the county clerk of the county the name of each person nominated for the office of delegate from the senatorial district in which the county, or any part of it, is included, and the names of all persons nominated for delegates-at-large.