Which of the Lutheran denominations leans that way? I know it's not ELCA, but I always get the Missouri Synod and the Wisconsin Synod mixed up.
Wisconsin Synod (WELS) is the most conservative. The Missouri Synod (LCMS) is pretty conservative on political and cultural matters but not too much into fundamentalist theology (they even issued a decree condemning that Left Behind nonsense)
Anyway, the latter seems to be strong in the rural counties just West of where BRTD is (and also along the parts of the Wisconsin border South of the Twin Cities), while the former seems to be strong in most (though not all) rural parts of the state. The ELCA is the strongest Lutheran denomination in all but a handful of counties though.
Most of those really conservative counties west of me aren't dominated by conservative Lutherans though, but ultra-conservative Catholics and Dutch Calvinists.