Maryland Code, Labor and Employment § 4-220

(1) the Mediation Service has certified as a bargaining representative after a consent election; or

(2) an employer currently recognizes as the bargaining representative without a consent election.

(1) shall be supported by at least 30% of the employees in the bargaining unit; and

(2) may not be submitted within 1 year after certification of the bargaining representative as a result of a consent election.

(c)(1) The Mediation Service shall investigate each petition submitted in accordance with this section to determine whether there is reasonable doubt that the bargaining representative in fact represents a majority of the employees in the bargaining unit.

(2) If, after the investigation, the Mediation Service determines that there is reasonable doubt, the Mediation Service shall order an election to resolve the issue.