What Were America's Views of Socialism from 1949-1965?

From 1937 to 1948, Gallup routinely included "socialist" as an option alongside "Republican" and "Democrat" when measuring Americans' party ID, typically finding about 1% identifying as socialists. This wasn't the heyday of U.S. socialism, which arguably occurred earlier in the century when socialist candidates for president won between 3% and 6% of the vote. Rather, it was the era of socialist icon Norman Thomas, who ran for president six times from 1928 to 1948 but never garnered more than 2% of the vote -- roughly consistent with Gallup's party ID measure for socialists.