Mont. Code § 13-36-202
When the reception of illegal votes is alleged as a cause of contest, it is sufficient to state generally that in one or more specified voting precincts illegal votes were given to the candidate whose nomination or election is contested that, if taken from the candidate, will reduce the number of the candidate's legal votes below the number of legal votes given to some other candidate for the same office. Testimony may not be received of any illegal votes unless the party contesting the election delivers to the opposite party, at least 3 days before trial, a written list of the number of illegal votes and by whom given that the party intends to prove at trial. This provision may not prevent the contestant from offering evidence of illegal votes not included in the statement if the contestant did not know and by reasonable diligence was unable to learn of the additional illegal votes and by whom they were given before delivering the written list.
§ 13-36-202, MCA