N.M. Admin. Code § 11.21.2.11
With the petition and at the same time the petition is filed, the petitioner shall deposit with the director a showing of interest consisting of signed, dated statements, which may be in the form of cards or a petition, by at least thirty percent of the employees in the proposed unit stating, in the case of a petition for certification, that each such employee wishes to be represented for the purposes of collective bargaining by the petitioning labor organization, and, in the case of a petition for a decertification election, that each such employee wishes a decertification election. Electronic signatures shall meet the requirements of the Uniform Electronic Transactions Act (Chapter 14, Article 16 NMSA 1978). Each signature shall be separately dated. Signatures dated more than one year prior to the filing of the petition not be considered when determining the sufficiency of a showing of interest or a determination of majority support, except for good cause shown. So long as it meets the above requirements, a showing of interest may be in the form of signature cards or a petition or other writing, or a combination of written forms and shall be presumed valid unless contradicted by the submission of clear and convincing evidence that they were obtained by fraud, forgery or coercion. No showing of interest need be filed in support of a petition for amendment of certification or unit clarification.
N.M. Admin. Code § 11.21.2.11