In 2016, Trump defied the experts and the media by putting together a winning coalition of independent voters (with whom he had a four-percentage-point margin), white women (+9), married voters (+8), suburban voters (+4), and non-college-educated voters (+7), according to the exit polling data. This coalition helped him win key battlegrounds states of Michigan, Wisconsin and Pennsylvania.
However, by this year the coalition had collapsed, with Democrats winning independents (+12), white college-educated women (+20) and married voters (+4). The usually Republican-leaning suburban vote was evenly split at 49 percent. There were telltale signs of weakness with married women in the 2016 election when Hillary Clinton managed to win them by two percentage points. (This was the first time in exit polling history that a Democrat carried this demographic.) In 2018, Democrats expanded their margins with married women to 10 points.
Another troubling sign for Republicans is that in 2016 married men supported Trump by a whopping 19 points, but they supported Republicans in 2018 by only three points. In 2016, Trump swept the Rust Belt states with the help from voters with incomes between $50,000-$100,000, winning them by three points; however, in 2018 this group flipped to support Democrats by five points.