One reason so many pundits have been so wrong about Trump, from the start, is that he appeals to people who are humiliated in school and afterwards by the kind of people who become pundits. Humiliated, left behind, disdained. Whatever his other appeals, Trump inspires folks who are sick of being condescended to, regarded as stupid, as losers; folks who want a strong-looking champion.
Paradoxically, Trump appeals in part to the half of all citizens who, unlike any of the kids in Garrison Keillor's Lake Woebegone, are below average. Trump is their winner, who hires (and fires) the highly educated guys who had always raised their hands in school, who went to good colleges, who get comfortable salaries, who feel they won the race, who occupy, for example, much of the media, the professions, even the managerial class. (They are found in both of the major political parties.) Trump can be seen as a champion of those who couldn't make it.
In a way, Hillary stands for the kids who were always brighter, got admitted, were knowledgeable (it was at Yale Law School that she met Bill). To people leaning to Trump, it doesn't matter that Hillary's well-prepared. It actually works against her. Trump's ethical lapses are forgiven, because he sticks it to those who felt superior in school, who seem or actually are arrogant. These Trump supporters will excuse anything except weakness and, to some extent, recklessness.
The election will be decided by people who want a champion who seems strong, but who fear obvious recklessness. That is Trump's big weakness, more than rage against people who are different than us, than his ignorance, than his ethical lapses, than his racism. His weakness is that he's characteristically reckless. Hillary's campaign has been asking, would you give this man the nuclear codes? It could also ask, more generally, do you want public policy in such reckless hands?
In a nation founded on the claim that all people are created equal it's awkward to mention any of the senses in which this is manifestly not the case. People are not equal in their wealth. In fact, economic inequality has become gross. And people are not equal in their abilities. For example, some are born smarter. Again, it's sobering to realize that about half of the population is below average. High intelligence is a genetic gift, not more merited than a big inheritance. Of course it can be refined, through hard work. But it starts as a gift.
In European thought, there is a tradition of analysis in terms of resentiment. Philosophers discuss this concept in such thinkers as Kierkegaard, Nietzsche, Scheler, Weber, and Deleuze. As you'd expect, the philosophy gets complex. But as applied to the 2016 presidential election, just think of the kid at school who always raised his or her hand, who now writes denunciations of racists, bigots, misogynists, and xenophobes (expecting his or her readers to know this means hatred of whom? Of Mexicans, say, and Muslims).
Several writers have got close to comprehending resentment in US politics. Their analyses are valuable. For example, Arlie Hochschild in Strangers in Their Own Land brilliantly explores the feelings of those who resent other people cutting into line, as Reagan's "welfare queens" were said to support illegitimate kids on the backs of the taxpayers, drive expensive cars, etc.
It seems paradoxical that losers in our socio-economic system would rally behind a figure such as Trump, who disdains losers and, even if his assets are far less than he claims, is a clear winner, at least in terms of wealth. Yes, he satisfies the urge for toughness. Yes, he articulates the rage of those for whom the system has not been working, workers whose jobs have been exported. But above all, he expresses their long-time rage against the liberal elite that disdains them, regards them as deplorable.