What is the ultimate left-wing novel?

Isaac L. writes to me:

I am hoping you and your readers can help settle an issue. I am a left-leaning voter.  A conservative friend and I recently discussed Atlas Shrugged, which he said was the ultimate right-wing novel. He challenged me to point him towards a left-wing novel that does for that side of politics what Rand does for the right. I think the book needs to do two things: justify the welfare state and argue the limitations of the invisible hand. While I can think of lots of non-fiction texts, I am drawing blank on fictional offerings.

Do you or your readers have any suggestions? Any assistance would be greatly appreciated.

What jumps to mind is Steinbeck's Grapes of Wrath, but if you read the request carefully it does not qualify.  Here is a list of thirty famous left-wing novels, heavy on the mid- to late nineteenth century.  There is Bronte, Dickens, Hugo, Sinclair, Zola, Gorky, Jack London, and Edward Bellamy.  None of these books is as analytically or philosophically comprehensive as the novels of Ayn Rand. 

I would say that the story per se is usually left-wing, in both good and bad ways.  It elevates the seen over the unseen, can easily portray a struggle for justice, focuses on the anecdote, and encourages us to judge social institutions by the intentions of the people who work in them, rather than looking at their deeper and longer-term outcomes.  Precisely because the story is itself so left-wing, there won't be a definitive example of the left-wing novel.  Story-telling encourages context-dependent thinking, although not necessarily in an accurate manner.  One notable feature of Atlas Shrugged is how frequently the story-telling stops for a long speech or an extended dialogue, in order to explain some first principles to the reader.