Each political party shall hold a state convention biennially on a date to be fixed by the state central committee but not later than September 1. Candidates for elective offices may be nominated at such conventions pursuant to section 32-627 or 32-721. Such nominations shall be certified to the Secretary of State by the chairperson and secretary of the convention. The certificates shall have the same force and effect as nominations in primary elections. A political party may not nominate a candidate at the convention for an office for which the party did not nominate a candidate at the primary election except as provided for new political parties in section 32-621. The convention shall formulate and promulgate a state platform, select a state central committee, select electors for President and Vice President of the United States, and transact the business which is properly before it. One presidential elector shall be chosen from each congressional district, and two presidential electors shall be chosen at large. The officers of the convention shall certify the names of the electors to the Governor and Secretary of State.