Unlike in Europe where socialist and communist parties have had sizeable voter support, historians have long noted and puzzled over their lack of electoral support in the United States, a part of the original meaning of the concept of American exceptionalism.
The highpoint of American socialist voting on a national level was the 1912 election, when Eugene V. Debs, the Socialist Party's candidate, received 901,551 votes, 6% of the total. It was downhill from then on, that is, until 2016 when in the Democratic Party primary Bernie Sanders, a self-described socialist, received 13,168,222 votes, nearly fifteen times Debs' total.
The comparison is of course not exact. The 2016 electorate is a lot larger than that of 1912 since the national population is a lot larger. But even in proportionate terms, Sanders broke Debs' record. If the November percentage turnout of registered voters is the same as that of 2012, Sanders 13 million plus votes will represent 9.8% of that total, which is greater than Debs' 6%. We can also assume that had Sanders beaten Clinton and gone on to be the party's candidate those 13 million plus votes would have expanded greatly.
But while Sanders was a socialist and, to his credit, did not shy away from the label despite the taboo that burdens it carries in American politics, he ran as a Democrat and not as the candidate of an actual socialist party, as did Debs.
Further, the platform that Debs ran under was substantially to the left of that of Sanders. That platform opened with a ringing denunciation of capitalism: "The capitalist system has outgrown its historical function, and has become utterly incapable of meeting the problems now confronting society." It then went on to propose, among other things, "the collective ownership and democratic management of railroads, wire and wireless telegraphs and telephones, express service, steamboat lines, and all other social means of transportation and communication and of all large scale industries."
Sanders had no such total denunciation of capitalism. He called for campaign finance reform, universal healthcare, and free college tuition among other proposals--all important but far short of what Debs and his Socialist Party were calling for. Sanders essentially was trying to bring the United States up to the social standards of European capitalist countries. He was not calling for the abolition of capitalism as such, as was Debs.
But despite not being an exact comparison, Sanders' 13 million plus votes was a remarkable achievement. It may have finally broken the socialist taboo, conditioned into a population by decades of antisocialist and anticommunist rightwing and often elite sponsored crusades.
To the astonishment of many, including on the left, the Sanders campaign proved immune to socialist-baiting. Governor Martin O'Malley indulged in a bit of it in an early debate, no doubt thinking of it as a silver bullet. But Sanders' popularity only grew. To the consternation of O'Malley and Clinton, what was supposed to be only a fringe candidacy that could easily be dispatched by socialist baiting was turning into a serious threat to the establishment.
Sanders then delivered a speech at Georgetown University, taking on the issue of socialism directly. What he had in mind, he said, were quite reasonable social protection reforms similar to those already adopted in Denmark and other European countries. He did not call for, like Debs in 1912, abolishing the capitalist system itself.
While all eyes are now on the political irrationality of Trump, what may turn out to be more remarkable for future historians is that another candidate found a way to make quite rational socialist ideas, if not full blown socialism, attractive to many Americans.