I like to point to one of the most successful Socialist parties that ever existing in the USA: The Socialist Party of Milwaukee. They got 3 mayors elected and effected actual change.

Part of the Socialist Party’s lasting success in Milwaukee can also be attributed to their pragmatism, Gousha says. Daniel Hoan made a point to exist within a capitalist free market system, they were fiscally conservative, and they worked with other parties to accomplish their goals.

Their pragmatism drew criticism from other socialists around the country, who called Milwaukeeans “sewer socialists” for not being revolutionary enough, according to Gousha.

"As Gene Zeidler said, 'The socialists of Milwaukee took that as a badge of honor. And they said, well you may think we need to be more revolutionary but you could not be elected dog catcher and we’re winning elections,’ " Gousha notes.

Article in question.