According to Marx, only the proletariat is capable of a revolutionary transformation of society, not because people in the proletariat are somehow better, but because the contradictions of bourgeois society create the proletariat — and only the proletariat — in ways that will eventually make them capable of revolutionary transformation. Only when the proletariat has lost everything under capitalism will they find the will and the power to overthrow capitalism.
The bourgeoisie has been far more clever than Marx expected in clinging to power, but the contradictions remain, and for a variety of reasons, the bourgeoisie is running out of tricks.
The proletariat must, however, learn to seize power, and learn to exercise it. What makes them a revolutionary class does not make them a good ruling class: there is nothing about the proletariat that makes them especially wise, clever, or efficient. And thus with any ruling class: the landed aristocracy and the bourgeoisie had to learn to rule as well. There is no way to learn how to actually take power but by trying and failing to take it; there is no way to learn to actually rule without trying and failing to rule.
The 2016 Presidential election raises some interesting issues.
First, neoliberalism is facing real problems. Although he's a racist (or playing one on TV), his racism is not why Donald Trump is popular. He's popular because he's anti-neoliberalism. And if he does beat Clinton, Trump will beat her precisely because he's anti-neoliberalism, at least on paper. (Trump doesn't have the will to actually fight neoliberalism as President.)
Sanders should be beating Clinton like Trump is beating Cruz, right?. He should be beating her even more soundly: the bourgeois left is supposedly more against neoliberalism than the right, n'est ce pas? Hardly. Neoliberalism is a creature of the bourgeois left, not the right. The bourgeois right is much more mercantilist/realist than neoliberal. Socialists should never count the bourgeois left as allies; the bourgeois left would rather risk fascism than socialism.
There is nothing about the proletariat that automatically disposes them to socialism. When they are being oppressed, they will pick whoever offers them the best story about escaping their oppression. The bourgeois right and the fascists are telling a better story than the neoliberals and the socialists. What is encouraging about Trump's popularity is that the proletariat is starting to fight back, on its own terms and not on the terms dictated by the neoliberals. They are fighting back poorly, unwisely, ineffectively, but they are fighting.
It really doesn't matter whether Trump or Clinton wins the election. Both will kill a bunch of brown foreigners and black Americans. The economy will continue to stagnate and decline under both. Neither will do shit about global warming. People in Flint will still drink filthy water. We will continue to imprison people, especially black people, in numbers that would make Stalin blush. Middle class white women will probably do marginally better under Clinton; middle class white men will probably do marginally better under Trump, but everyone not in the top 0.1%, the actual ruling class, or the top 10%, their servants, will be worse off four years after the election.
Indeed, it is possibly better if Trump wins the election. First, Trump is a buffoon, without the will to actually be a real fascist. If he's elected, he will quickly expose the emptiness of the nationalist/realist agenda. If Clinton wins (or if Trump is denied the Republican nomination), then the forces of reaction will just get stronger, and whoever follows Trump could well have the will to real fascism.
Socialists have an historic opportunity, one not seen since the aftermath of the First Global Imperialist War (a.k.a. WW I). Neoliberalism is collapsing, and the forces of reaction have only (for now) a clown to represent them. We have the perfect opportunity to tell a better story (better in no small part because it's true). Neoliberalism is weak, and, losing hegemony, the American neoliberals can no longer buy off even the labor aristocracy, much less the proletariat as a class.
Trump's weak-tea fascism-lite, if quickly exposed, will not have the force to satisfy the proletariat. However, if current conditions are a great opportunity for socialism, they are a great opportunity for real fascism, which holds a lot of appeal for the still-maturing proletariat.