The DFL is a legitimately superior political party - probably one of the best examples of any state Democratic Party in the country - compared to the state GOP, complete with deep local roots all across the state and a culture that is synonymous with the state itself.
This gives it a natural advantage compared to neighboring states and has ensured that the GOP doesn't have a prayer unless there is a national blow-out and/or a very good GOP candidate. Even then, a GOP win in the state is going to almost always be under 50% and by a hair in terms of margin.
This. The DFL has done a good job of remaining competitive with rural whites. Only Trump's near-win combined with a bit of division between the urban and rural factions of the DFL allowed them to take the state legislature.
Also, Minnesota's population is more educated than other midwestern states, and slightly less white.
