Since its creation in 1892, the Socialist Party had endorsed woman's suffrage. This long and strong identification with the cause perhaps explains why many Americans associated suffragists with socialists.
In 1892, the fourth "political demand" of the Socialist Platform read, "Direct vote and secret ballots in all elections. Universal and equal right of suffrage, without regard to color, creed, or sex. Election days to be legal holidays. The principle of minority legislature to be introduced."
By 1912, the fourth political demand simply stated, "Unrestricted and equal suffrage for men and women."