Whenever congress proposes an amendment to the constitution of the United States, and proposes that it be ratified by conventions in the several states, the governor shall fix, by proclamation, the date of an election for the purpose of electing the delegates to such convention. Such election may either be at a special election or may be held at the same time as a general election, but shall be held at least as soon as the next general election occurring more than three months after the amendment has been proposed by congress.