A. In considering the sufficiency of a referendum petition the burden of proving that all signatures appearing on the page are genuine and that the signers are qualified electors of the county named on the page and are in all respects entitled to sign the petition shall be upon the sponsors of the petition, if it is apparent beyond a reasonable doubt to the secretary of state that twenty percent or more of the signatures on any one page thereof are fictitious, forged or otherwise clouded, or that the challenged petitioners were ineligible to sign the petition, which fact was known or could have been ascertained by the exercise of reasonable diligence on the part of the person soliciting the signatures on that page.

B. If the sponsors of the referendum petition refuse or fail to assume and meet such burden, the secretary of state shall reject the entire page and shall not count as petitioners any of the names appearing thereon.