If prior to the date when an ordinance takes effect, a petition signed by qualified electors of the city equal in number to 15 per cent of the total vote at the last regular municipal election is filed with the city clerk requesting that any such ordinance be repealed or be submitted to a vote of the electors, the ordinance shall thereby be prevented from going into operation. The council shall thereupon reconsider the ordinance at its next regular meeting and either repeal it or by aye and no vote reaffirm its adherence to the ordinance as passed. In the latter case the council shall immediately order a special election to be held thereon or submit the ordinance at the next regular municipal election, pending which the ordinance shall remain suspended.
If a majority of the electors voting thereon is opposed to the ordinance it shall not become effective; but if a majority of the electors voting thereon favors the ordinance, it shall go into effect immediately or on the date therein specified.