Before being filed, each petition shall be certified by an affidavit by the sponsor who personally circulated the petition. The affidavit shall state in substance that (a) the person signing the affidavit is a sponsor, (b) the person is the only circulator of that petition or copy, (c) the signatures were made in such person’s actual presence, (d) to the best of such person’s knowledge, the signatures are those of the persons whose names they purport to be, (e) the person circulated the petition in the manner provided by this act and (f) the person signing the affidavit, being duly sworn, on oath states that the statements of grounds for recall contained in the recall petition are true. In determining the sufficiency of the petition, the county election officer shall not count signatures on petitions not properly certified. The recall committee may file the petition only if signed by registered electors in the election district of the local officer sought to be recalled equal in number to not less than 40% of the votes cast for all candidates for the office of the local officer sought to be recalled, such percentage to be based upon the last general election for the current term of office of the local officer sought to be recalled. If more than one person was elected to such office at such election the number of signatures required shall be equal to not less than 40% of the votes cast at such election for all candidates for the office divided by the number of persons elected to such office.