I "borrowed" this title from José Ortega y Gasset's book Revolt of the Masses. It seems to me that there is an often-overlooked factor that is becoming increasingly evident in American politics: the mounting disaffection for the usual type of politician favored by the major political parties. Presently, Donald Trump is leading in polls for the Republican nomination; and Hillary Clinton is challenged by Bernie Sanders for the Democratic one. I don't know what will transpire when the primaries come on, but Jeb Bush is losing ground and other possible establishment candidates were less than inspirational.
As for Hillary, a common sentiment is, "In order for me to vote Democratic, must I vote for her?"
It seems to me that there has always been a strong Populist sentiment in our collective American DNA. While this is less evident at some times, on other occasions it might rear its scary head, at least as perceived by the Eastern elitists. Andrew Jackson rode into the White House on a strong populist platform; and this movement returned in the 1890's and early 1900's. While the Populists did not elect a President, they managed to influence laws reining in trusts, having pure food and drugs, ending the more severe abuses in child labor, controlling sexual exploitation, and eventually the forty-hour week.
Populism in those earlier manifestations stood for the little guy, for local government by consent rather than from above, and for resisting pressure from outside powerful others. Nowadays these outside sources of pressure are reified in the form of big business, the Eastern Establishment, the liberal academic elite, the mainstream media, and the preening popinjays of Hollywood. Not to mention Main Street!
I'll have to admit that they annoy me sometimes too.
But the people that are most disaffected are the working stiffs, particularly the ones who are just getting by. These are the same ones that feel threatened or put upon by this cabal of busybodies. They see the major parties as the tools of these elites and special interest groups when many of them see themselves as unrepresented. Because of this, they are open to the allure of the outsider with simplistic solutions.
Despite what political parties say, both are open to seeking blocs of votes that they can reliably count on. In some ways, this makes their job of pleasing the electorate easier: please a part of them. Make them a special interest group that they service! On the other hand, these groups have to be given some reasons for their continued support. In that way, both parties must cater to the groups they already have in the fold.
The Bubbas are often scorned by people considering themselves to be elite. Despite the Trumpees, they're not necessarily reactionary or racist; but they seemed to feel shut out of the American Dream and into the American Just Getting By. The fact is, their job security is very thin.
In short, there are a lot of people out there that felt that their concerns and problems were not taken into account, and some of them are scared. Rightly so. They might be prone to accept nostrums or pat solutions.