In the concluding pages of the novel, the change in Jack's views are represented by his repudiation of his 'Great Twitch' theory: 'But later, much later, he woke up one morning to discover that he did not believe in the Great Twitch any more. He did not believe in it because he had seen too many people live and die.' At this late point, via the metaphor of the Great Twitch, it is emphasized that Jack now has faith in people taking responsibility for their actions.
Willie Stark Hospital
When Willie gives the contract for the building work to Gummy Larson (as a pay off to stop MacMurfee blackmailing him about his son's affair and possible child),Willie's descent into the moral quagmire is complete. The hospital had symbolized purity up to this point; when Willie involves Larson, he no longer has any of the redeeming qualities which Jack could see in 'Cousin Willie'.
The sad, ironic aspect to Willie's dream is encapsulated in his final decision not to give Larson the contract after Tom is paralyzed. His assassination foreshortens any aspirations to return to 'goodness'.
All the King's Men: Metaphor Analysis