Make the Russian Revolution fail and you don't have Lenin asking the left-wing of the SPA, along with the IWW, to join the Comintern; which helped tear the party apart even while it still emerged from the war-time persecution with a large and growing presence in 1918.
Without the Red Scare of 1919 or the party split over Comintern entry, the Socialists will in the fullness of time, just as even in OTL Debs was pardoned by President Harding for his imprisonment on sedition charges for opposing the draft, benefit from their opposition to entry in the Great War and continue to grow from their high-water mark.
Without the Red Scare of 1919 or the party split over Comintern entry, the Socialists will in the fullness of time, just as even in OTL Debs was pardoned by President Harding for his imprisonment on sedition charges for opposing the draft, benefit from their opposition to entry in the Great War and continue to grow from their high-water mark.