"In 1948 the two-party duopoly smeared and suppressed the pro-labor efforts by the Progressive Party and its presidential candidate, former Vice President (under Franklin Delano Roosevelt) Henry Wallace. This was followed by more onerous restrictions on state ballot access and exclusions of third parties, enacted by both the Republicans and Democrats, that further stunted competitive choices of candidates and agendas."
January 1, 1970
https://en.wikiquote.org/wiki/Henry_A._Wallace