If prior to the date when an ordinance or resolution takes effect a petition signed by qualified electors of the city equal in number to fifteen percent of the total vote at the last regular municipal election be filed with the city clerk requesting that any such measure, or any part thereof, be repealed or be submitted to a vote of the electors, the said measure shall thereby be prevented from going into operation. The council shall thereupon reconsider the said measure at its next regular meeting, and either repeal the same, or repeal by the petitioners, or by aye and no votes reaffirm its adherence to the measure as passed. In the latter case the council shall immediately order an election to be held thereon, pending which the ordinance or resolution shall remain suspended. If a majority of the voters voting thereon are opposed to the measure it shall not become effective; but otherwise it shall take effect immediately or on the date therein specified.