In the film, Morris turns out not to be the upstanding family man he portrays himself to be. He is neither noble nor selfless and ultimately all of the pontificating he does about values proves to be lip service to the public so he can get what he wants. He energizes crowds by saying what they want to hear, not what he believes in or what he intends to do.
On basic level, March takes on the dishonesty of politicians and the lying and cheating they all do to get to the top. In that sense it's an old story - politicians lie. We all know that. The interesting piece of this film, however, is when it's seen as an allegory to the current administration and leadership. Morris is clearly meant to be an Obama figure (the imagery aligns him as such in almost every way down to the copycat iconic "Hope" poster). Is this how Clooney has come to see Obama? In the last 3-ish years of his presidency (even less if you stop counting when the script was written) has Obama become such a major failure that even his staunchest Hollywood supporter sees him nothing more than a liar?
Clooney has been an ardent supporter of President Obama and in this film he seems to be conveying his disappointment, possibly in Obama himself, but more likely in the political system as a whole. Not to say that he believes that Obama has done some of the terrible things Morris has done to get to the top. Rather it seems to be saying that no matter how impressive a candidate starts out as, they will inevitably disappoint they're supporters. There is no nobility or altruism in this field and anyone who thinks otherwise will be disappointed.
This film does a good job at depicting what could be a real life political cover-up and explains the inner-workings of campaign strategists and how they interact with the press and the campaign managers from other candidates. A stellar cast rounds out the other supporting characters - Paul Giamatti, Philip Seymour Hoffman, Marisa Tomei and Evan Rachel Wood all shine in their roles bringing depth and life to their characters. At times it seems some of the lengths they go to might not be plausible, but really I wouldn't put it past anyone running for office to be as sleazy as the movie makes them out to see, despite the shiny exterior. And that's ultimately the message the film is going for.