Socialism is still really unpopular in the United States
It has long struck me as puzzling that Bernie Sanders refers to his ideology — which I would characterize as social democracy or even just welfare state liberalism — as democratic socialism, a politically loaded term that seems to imply policy commitments Sanders hasn't made to things like government ownership of major industries.
In the context of the Democratic primary, the socialist branding seems to have offered Sanders some upside — both branding him as more than just another politician and earning him enthusiastic support from a number of politically engaged people who seem to really be socialists and who have poured their scorn for liberals and liberalism into a drumbeat of criticisms of Hillary Clinton.
Against this, though, one has to weigh the reality that socialism is really unpopular in the United States.
Any form of left-of-center politics in the United States, frankly, is going to have a problem with the fact that "the federal government" is viewed so much less favorably than cuddly targets like "small business," "entrepreneurs," and "free enterprise." Even big business does better than the federal government. And both big business and capitalism do far better than socialism.
This is one of several reasons Democratic Party leaders, including superdelegates, are largely unmoved by arguments grounded in current head-to-head polling matchups that show Sanders doing even better versus Trump than Clinton does: A race that could be framed as a choice between capitalism and socialism would be very unfavorable terrain for the Democratic nominee.
Indeed, Sanders himself seems implicitly aware of this and is always quick to say that by "socialism" he means something like the kind of expansive welfare state that exists in Denmark. The Nordic social model really does have a lot to recommend itself, but it's not generally regarded to be socialism — large, private business corporations owned by shareholders, including by Denmark's prime minister and other relevant figures, are a very prominent aspect of Danish economic life.
All in all, it's a good reminder that despite Sanders's unexpectedly strong performance in the Democratic primaries, the concept of socialism remains strikingly unpopular among the larger electorate.