Unless the Mediation Service receives a timely objection to a petition, the Mediation Service shall approve the petition to enter into a consent election agreement. The Mediation Service shall investigate each timely objection to a petition from a labor organization that purports to represent a substantial number of employees whom the petition affects. If, after the investigation, the Mediation Service determines that the labor organization seems to represent a substantial number of employees whom the petition affects, the Mediation Service shall place the name of the labor organization on the official ballot to be used in the consent election.