There shall be no primary election for City officers. Nominations for the office of Mayor and Councilman-at-Large shall be made by petitions signed by not less than fifty nor more than one hundred registered voters. Nominations for ward councilmen shall be by petition signed by not less than twenty-five nor more than fifty registered voters, residents of the ward. Candidates for the office of ward councilman shall be residents of the ward they seek to represent at the time of filing their petitions. All petitions shall be on the standard forms for the use of nonpartisan candidates for such offices; group petitions shall not be used. Petitions shall be filed with the Board of Elections at least ninety days before the day of election.