More of the same didn't cut it for the American middle class this November, ... and so the Obama voters went to the Republicans, as Hillary Clinton failed to impress onto the middle class any sort of vision they can relate to.
Per Pew Research, out of 57 'solidly middle-class areas' examined, "In 2016, Trump successfully defended all 27 middle-class areas won by Republicans in 2008. In a dramatic shift, however, Hillary Clinton lost in 18 of the 30 middle-class areas won by Democrats in 2008."
So the "deplorables" turned out to be middle-class voters and they clearly heard Hillary Clinton applying a new descriptive term to them. The term they did not quite embrace.
Now, if I were an adviser to the Democratic Party, I would start by putting its leaders in front of a mirror and ask them to point out every little wrinkle and crease in their faces that makes them so publicly loath middle-class as to endorse a candidate that called them 'deplorables'. Step one of the multi-year journey toward rebuilding the party will then be accomplished.
Rest of Pew Research analysis here.