Ever since Wisconsin Gov. Scott Walker's controversial tenure began in 2011, anybody who follows state politics has been repeatedly made aware of the deep political divisions in the state.

As the Milwaukee Journal Sentinel displays in a fascinating map, the Milwaukee area is particularly polarized. The overwhelmingly Democratic city is surrounded by solidly Republican suburbs. Among the nation's largest 50 metro areas, only New Orleans has a wider gap in partisanship between its urban and suburban population.

Looking at the dark blue wards in the central city and the bright red ring around it, it's hard to blame the state's largest paper for its decision nearly two years ago to no longer endorse candidates for public office. In that media market, it's hard to pick a candidate without deeply upsetting a significant share of your readers.