And F. Scott Fitzgerald may be the worst “left wing” writer in the world even if you could categorize him as such. He tried his hand at it in the 1930s because he was being hounded by Hollywood leftists and communists (the awful wife of Nathaniel West comes to mind) and he was desperate for money to help clear up his debts and provide for his wife. Possibly America's greatest writers, I'm surprised you would single him out.
P.S.: the other writers you mention are pretty damned good too.
I was quoting another site.
Miller’s stuff has held up a lot better than some of the more overt agitprop from the era like Clifford Odets. I saw a production of ‘Awake and Sing’ and it’s quite dreary. A big influence on Miller I think.