The newest episode of Vox's excellent new podcast The Weeds starts with one of the best discussions of 'money in politics' that I've yet come across. They make three key distinctions that, when taken together, reveal the complexity of the issue.
1. Money in politics =/= interest groups. Interest groups have many other channels of influence (votes, organization, social clout) besides pure money. This suggests that 'getting money out of politics' wouldn't necessarily provide a more responsive or democratic government.
2. Interest groups and money often reduce ideological coherence by structuring political incentives. This increases pragmatism in politics and reduces pure partisanship. The idea of money and interest groups as a moderating influence in politics is fascinating: reduce the power of these forces, and you might increase the relative power of political junkies who tend to be much more partisan.
3. High salience increases an issue's partisanship and reduces the efficacy of money and interest group influence. This idea is nothing new, but the widespread acknowledgement of its validity is changing political strategy, in my view. Once an issue becomes partisan, political incentives to deprive the opposition of a 'win' override policy preferences. What's really screwed up here is that the solution--to craft policy in secret--provides a richer environment for interest group influence.