Nominations of candidates for president and vice president of the United States, other than by a major political party, may be made at a convention conducted not earlier than the first Saturday in May and not later than the fourth Saturday in July in the year that president and vice president appear on the general election ballot. A minor political party may hold more than one convention but in no case shall any such party nominate more than one candidate for president or more than one candidate for vice president. To be valid, a convention must be attended by at least one hundred registered voters, but a minor party or independent candidate holding multiple conventions may add together the number of signatures of different individuals from each convention in order to obtain and submit to the secretary of state the signatures of at least one thousand registered voters of the state of Washington.