Candidates for members of the constitutional convention shall be nominated by nominating petitions. The nominating petitions shall be in writing and addressed to the Secretary of State. The nominating petitions shall be signed by not less than five percent of the qualified electors of the legislative district. The percentage shall be based on the number of electors voting in the legislative district at the last preceding general election. In no case shall the number of signers to the petition be less than one hundred.