In today's America, while there are actually a multitude of political parties, there are, in fact, only two political parties that matter, and these two parties effectively control national, state, and local election politics. While there may yet come a time when a viable third party comes to fruition in America, again; in recent decades, the only time that any other political party has been relevant, has always been based around a specific, particular candidate, such as George Wallace, or H. Ross Perot, as compared to the political party, that those candidates are running under, proper.
Incredibly, in 1912, Eugene Debs, in a Presidential run as the Socialist Party of America's candidate, garnered nearly 1 million votes, which was good enough for 6% of the national vote, in which the winner, Woodrow Wilson, received less than 42% of that national vote. As important as Debs run was, it should be noted, that in the 1910s there were two Socialist candidates that won office as United States Representatives. Additionally, as reported by Wikipedia.com, during this time period, "…dozens of state legislators, more than a hundred mayors, and countless lesser officials…" were elected, that were members of the Socialist Party.
All of the above, makes the very salient point, that certain elements within this society, have for an extended period of time, been frustrated with the capitalistic system as practiced in America, in which, quite clearly, there are a few outsized winners, that benefit themselves along with their ilk; while leaving a substantial portion of Americans with little or nothing to hold onto, and thereby a desire by those so left out to be part of a political system that would properly allow them to have some semblance of a life, in which those that work diligently would be able to thereby harvest fairly what they have duly sowed. So too, typically unrecognized, is that those that are the richest amongst us, , far too often, have obtained that money and power, by virtue of their ruthless exploitation of others, favoritism, connections, and the gaming of the system, to favor their interests at the expense of the general public.
The bottom line is that the people, in whole, are not stupid, and recognize implicitly as well as explicitly that the system as practiced in this country is wholly unfair. Again and again, the change so promised to those people, never comes to bear, and therefore, in absence of any toehold of significance in this nation, they gravitate to that which supports the common man in achieving noteworthy goals of owning something of significance, as well as having enough self-sufficiency, to be able to be their own person.
Those political candidates of today that appeal to socialistic credos, will continue to have their relevancy, because the underclass of America is now, and has been, dismissed and marginalized for so long, that such is itching to have their fair day in this country of supposed liberty and opportunity. In a nation, in which each person of age is entitled to one vote, there is only so long that a small minority can successfully rule the roost, without such a country devolving into a de facto police state. Those that are socialist today in their sentiments are in harmony with those that were socialist back then, because each of these people desires a life worth living, and this of all countries, should be able to fairly provide that for its entire people.