Brexit and Trump and Syriza and Bernie and all the rest of it point to the collapse of the middle class across the industrialized world more than anything else.
The middle class is doing fine. It's the working class that has been suffering, and they are the ones who voted for Trump in overwhelming numbers in swing states.
Sure, whichever. The terms are imprecise and many of the people we're talking about probably could have reasonably considered themselves middle-class in the past.