The thing that may fool people about MN is that it was (relative to the national average) kind of artificially Democratic in the 80's because of (a) Walter Mondale and (b) its relative lack of urban ghetto/crime/white flight-type problems which were highly salient in that decade. So certainly in a broad sense it has trended Republican since then. But since then it's been pretty consistently around a couple of points more Democratic that the national average in all elections, give or take a point or two.
b is a good point I've actually never thought of before.
I think this is one of the most important factors behind voting patterns in the 80's. Compared to now, for instance, Dukakis's vote looks quite weird: how do you lose IL, MI, MD, and southeast PA while winning WV, southwest PA, the upper midwest and the Pacific northwest? Well, compare: Chicago, Detroit, DC, Baltimore & Philly are all majority-minority and had major problems with inner city riots and depopulation. Whereas Pittsburgh, Minneapolis-St. Paul, Portland and Seattle are all majority white, plus in resource extraction areas (Appalachian coal, the MN Iron Range and the northwestern timber areas) the nature of the industry forces an unusual pattern of union Democrats in small white towns. So people won't be so afraid of Willie Horton etc.
