Mont. Code Ann. § 13-12-204
13-12-204 Method of correction of ballot
13-12-204 . Method of correction of ballot. If an appointment has been made to replace a candidate, as provided in 13-10-326 , 13-10-327 , or 13-10-328 , or if a candidate for lieutenant governor has been advanced to the candidacy for governor, as provided in 13-10-328 , after the ballots have been prepared but before the election, the election administrator may:
(1) correct the ballot in a manner consistent with rules adopted under 13-12-202 ;
(2) have the entire ballot redone; or
(3) have a separate ballot prepared only for the office for which the new candidate is a candidate.