Mont. Code Ann. § 13-37-204

A candidate, political committee, or joint fundraising committee may remove the candidate's or committee's campaign or deputy campaign treasurer. The removal of any treasurer or deputy treasurer must immediately be reported to the officer with whom the name of the campaign treasurer was originally filed. In case of death, resignation, or removal of the candidate's or committee's campaign treasurer before compliance with any obligation of a campaign treasurer under this chapter, the candidate, political committee, or joint fundraising committee shall appoint a successor and certify the name and address of the successor as specified in 13-37-201.