The secretary of state may refuse to file any initiative or referendum petition being submitted upon any of the following grounds:
(2) That the petition clearly bears insufficient signatures.
(3) That the time within which the petition may be filed has expired.
In case of such refusal, the secretary of state shall endorse on the petition the word "submitted" and the date, and retain the petition pending appeal.
If none of the grounds for refusal exists, the secretary of state must accept and file the petition.