Quite the opposite, throughout the movie, the theme remained to be "the gears are continually turning". Stephen has settled with the idea that idealism is politics is folly, and the candidate is just another guy and not "the one" hence the playing of "integrity matters, doing the right thing matters" in the background by Governor Mike Morris.
There isn't any drastic change in his character and if there was, he would have taken the alternative route of going to other consulting firms.
The meaning of the end reinforces the true disingenuous nature of what is a political campaign; building stories and playing on words to give the "appearance" of integrity in a candidate.
(Whether that's true in reality is another thing altogether)