1) Calling Washington corrupt devalues the word "corrupt." Dhaka is corrupt. Moscow is corrupt. Washington is dysfunctional, but not corrupt. Americans couldn't even process what an actually corrupt government would look like. They have no frame of reference. There is an important reason to not throw the word "corrupt" around willy nilly. If you convince Americans that this is as bad as it gets, they will become apathetic. After all, what's the point of doing anything if the government is already in such a huge hole there is no climbing out? Overplaying the "corruptness" of Washington draws eyeballs, but it ultimately undermines your overall goal.
2) Blaming money is a diversion. Talking about how "money corrupts the political system" ignores the problem. And the problem is this: the people agree with the corporations. On nearly any substantial political issue you'd like to name, there is not just money but votes on the pro-corporate side. If you want to shut down heavily-polluting and destructive coal power in this country, you have to fight not just the corporations, but all of the people for whom coal is a way of life. When Obama and Romney got on stage during the last debate to see who could get the coal industry's dick the deepest down their throat, they didn't do it because of the money the coal industry donated to their campaigns.[1] They did it because ordinary Pennsylvanians,[2] treat attacks on the coal industry as an attack on their livelihoods and their way of life. If you want to break up or regulate big corporations, you can find plenty of ordinary people to say: "the government shouldn't be messing with those businesses."
The only things that attract broad political opposition are things that don't matter (e.g. "earmarks" which account for approximately 0% of the budget). The only things that attract universal condemnation are wiggle-words like "corruption" and "pork" and "wasteful spending" on which everyone can project their own viewpoint and still act like they are in agreement with everyone else.
Lessig goes wrong from the very first sentence of this article: "We Americans are disgusted with our government." The basic issue is that people aren't discontent with our government. Sure they have a general distaste for it in the same way they have a general distaste for going to the dentist, but if you sit down and really look at the issues, the big questions of governance, there is no collective consensus about doing anything important differently. Bigger military or smaller military? Tougher on crime or more protective of individual rights? Less religion in the public sphere or more? More taxes or less taxes? More privatization or less privatization? More regulation or less regulation? If you get out of Boston or San Francisco, you can find tons of ordinary people around you to take either side of each of these debates.
What you can't find much if any of are substantial, meaningful issues that everyone agrees should be changed, in a specific way, but which are nonetheless held to the status quo by our "corrupt" government. That is real corruption.
[1] People dramatically overestimate how much money corporations actually give out. First, it's illegal for corporations to donate directly to candidates. Second, both Obama and Romney raised more direct contributions than the amount of money spent on their behalf by PAC's and non-profit organizations. And direct contributions can and are limited and not affected by Citizens United.
[2] And Pennsylvanians are really important! There is a joke: why did God put all of our oil under Saudi Arabia? Well, god put all of our swing votes in Pennsylvania, Ohio, Iowa, etc.