Trilling's novel, which dates back to 1947 and the years in which the Cold War was emerging, complements the critique of Popular Front politics and Stalinism that the author and other intellectuals previously tied to Communism and Marxism developed in their essays in journals such as The Partisan Review, Commentary and Dissent. The Middle of the Journey targets the root of Popular Front politics: the coalition between the working class and middle class intellectuals. The character of Gifford Maxim challenges the Crooms' idealized views of the working class and he is proved right when their handyman, Duck Caldwell, kills his daughter. Although they are not card-carrying members of the Communist Party, the Crooms are "fellow travellers", middle-class people who believe in the Marxist and Socialist project and are willing to turn a blind eye to Stalinist crimes. Caldwell's brutal if accidental killing of his own daughter shows the lack of wisdom in the Crooms' idealized views of the working class and represents the climax of the book.
For an opposite view of Popular Front politics and culture from Trilling's, one that emphasized the Cold War bias in such negative assessments as Trilling's, you can look at the first link below which takes you to a preview of Michael Denning's study The Cultural Front (1997).