Any abortion restrictions this Republican trifecta rams through will be met with a vengeance.
Montana in the 2020's could be similar to Kansas in the 2010's: state accustomed to centrist/center left executives with GOP-dominated legislatures elects a staunch conservative governor who passes reactionary policies that tarnish the party's brand at the local level.
To build off of this point, the MT Democratic Party also has a very strong infrastructure already built in (much stronger than what the KS Dems have), so the MT GOP would be in a much bigger hole than the KS GOP was in, if this actually happens.