(1) Except as otherwise provided in this subsection, the board of state canvassers shall make an official declaration of the sufficiency or insufficiency of a petition under this chapter at least 2 months before the election at which the proposal is to be submitted. The board of state canvassers shall make an official declaration of the sufficiency or insufficiency of an initiative petition no later than 100 days before the election at which the proposal is to be submitted. The board of state canvassers may not count toward the sufficiency of a petition described in this section any valid signature of a registered elector from a congressional district submitted on that petition that is above the 15% limit described in section 471. If the board of state canvassers declares that the petition is sufficient, the secretary of state shall send copies of the statement of purpose of the proposal as approved by the board of state canvassers to the several daily and weekly newspapers published in this state, with the request that the newspapers give as wide publicity as possible to the proposed amendment or other question. Publication of any matter by any newspaper under this section must be without expense or cost to this state.

    (2) For the purposes of the second paragraph of section 9 of article II of the state constitution of 1963, a law that is the subject of the referendum continues to be effective until the referendum is properly invoked, which occurs when the board of state canvassers makes its official declaration of the sufficiency of the referendum petition. The board of state canvassers shall complete the canvass of a referendum petition within 60 days after the petition is filed with the secretary of state, except that 1 15-day extension may be granted by the secretary of state if necessary to complete the canvass.