I've never been to Wisconsin but I've never understood how a state that seems pretty middle-of-the-road and elects some fairly decent politicians also goes 50-50 for Trump and produces some of the most unhinged extremists we've seen in state office.
I'll do some cliffs because I can get kinda long-winded on this:
There are a few blue pockets around the major population centers - namely Milwaukee, Madison, Racine, La Crosse and Eau Claire. The rural/suburban pockets surrounding those areas are almost universally red. There's a bad and misguided split between the urban population centers - especially Milwaukee (mostly because that's where the Black folks are) - and outstate. The state is actually purplish in its voting trends, but gerrymandered to the point that the legislature and state Supreme Court will be GOP controlled for a long time. It's also worth noting the state Democratic party was inept for multiple election cycles, which partially led to this.
As GOP goes, of course, so do those red voters. Most of those red voters are straight-up hayseeds or suburbanites terrified of Milwaukee and Madison. Right now, it takes any combination of Trump-style rhetoric, using Milwaukee as a boogeyman/racism and dark money (depending on the race) along with help from the state Supreme Court and legislature to elect and keep those extremists in office. That's how an idiot like Ron Johnson who has no business being elected can beat like a statesman like Russ Feingold and hold office so long. He married into money, but rubes will eat up that "aww shucks, I'm a patriot like you" act. Ditto for Scott Walker - he made a career out of sucking the government tit, but these goofies ate up his good 'ol boy routine.
Interestingly enough, there's a good shot a brotha (Mandela Barnes) might end up as the Dem senatorial nominee against Ron Johnson. We'll see how that turns out.