Elizabeth Warren appeared last night on The Daily Show and talked with Jon Stewart not about policy specifics but about the general phenomenon of corruption in Washington. In doing so, she got off a good zinger about how the system works "to make sure that the tender fannies of the rich and the powerful are always carefully protected."

But she also laid out a sophisticated understanding of the real way power and money intersect. It's not primarily about quid pro quo cash for favors. It's about whose voices get heard and what issues end up on the agenda. "The wind only blows from one direction," Warren said. "It only blows from the direction of those who have money." Yes, campaign contributions matter. But big interests have "invested in other ways," too. They've invested in paying attention to what happens and to having their agents show up constantly and make noise. Consequently, the concerns of the rich and powerful are present in "every rule that's written, in every conversation, in every discussion."

Watch it:

Warren's perspective on this is supported by my favorite book about influence peddling — Lobbying and Policy Change: Who Wins, Who Loses, and Why.

The authors show two things. One is that it's not true that the richest interest group always wins. Better-financed groups lose to less-financed groups all the time in DC. One big reason for that is that the American system is simply set up to make change very difficult. What normally happens is that the status quo wins, not necessarily the richer side.

But money does matter. Money matters because you have absolutely no chance of winning unless you can get on the agenda, and you can't get on the agenda unless you have money to spend. An ultra-rich interest group can be defeated by a merely rich interest group, but unless you can show up on Capitol Hill with some kind of sack of cash you can't get your voice heard at all.