Socialism is characterized by the Government owning all means of production, as well as farmland, mines and natural resources, and controlling the distribution of goods and all pricing; in exchange for this, the Government provides, universally and uniformly, a basket of goodies to meet the needs of the population.
When American politicians identify themselves as "Socialists," what they really want to do is to emulate the social democracies of Europe, which are basically CAPITALIST economies (private property, private farms, extensive entrepreneurial climate & relatively free markets), where government has taken upon itself (financed by the taxpayers) the burden of providing a large basket of goodies to the population, so that theoretically no one is homeless, starving, naked, or sick (for long).
So it's not a matter of Republicans calling these politicians (incorrectly) "socialists." This is what they incorrectly call themselves.
BTW Sweden and other often-mentioned countries are not Socialist, and their leaders bristle that such a characterization. If they did not have private property, large, successful private businesses, and relatively free markets, there would be no money to pay the taxes to pay for the large basket of goodies.
The folly of being an American Democrat/Socialist is that THE AMERICAN PEOPLE WILL NEVER PAY THE LEVEL OF TAXES THAT WOULD BE REQUIRED TO PAY FOR THE BASKET OF GOODIES, not to mention that such a "risky scheme" would be unconstitutional. And in my opinion, we do not have a sufficiently-strong work ethic to sustain such a system. In other words, if you provide, for example, a guaranteed annual income, half the ******* population will try to sign up for it. Which is also a growing problem in Europe, especially with the new immigrant hordes.