Section 7A. Except where otherwise provided by law, every nomination petition or other like paper of a candidate for a city office in a city wherein preliminary elections for the nomination of candidates for such office are held shall be submitted, on or before five o'clock in the afternoon of the fourteenth day preceding the day on which it must be filed, to the registrars of the city. In each case the registrars shall check each name to be certified by them on the nomination petition or other like paper and shall forthwith certify thereon the number of signatures so checked which are names of voters both in the city and in the district for which the nomination is made, and only names so checked shall be deemed to be names of qualified voters for the purposes of nomination. The registrars need not certify a greater number of names than are required to make a nomination, increased by one fifth thereof. Names not certified in the first instance shall not thereafter be certified on the same nomination petitions or other like papers.