"Is that normal?"
My husband was born in Montana and he just said Montana is primarily democratic because it is a strong union state (Miners)
The mining industry comprises most of the west, notably around Butte. Generally for all intents and purposes, at the state level, Montana is cut in half, it's redder on the eastern side and bluer on the western side, which is reflective in the Senate candidates and the lone Representative. Generally in national elections (President) Montana is safely in Republican hands.