Anyway, I am one of those rare folks who thinks there's not enough money in politics. Or at least that we shouldn't worry about the money that's already there. The Center for Responsive Politics (a pro-reform group) estimates that total Federal direct election spending reached $6 billion in 2012[1]. Even if "shadowy groups" spent twice that over again (they didn't), that's $18 billion worth of spending to influence the future of a $3.6T government regulating a $15T economy.
To put it another way, $18B is less than half the annual revenue of the Coca Cola company, or only 6x what Americans spend on scented candles every year.
[1] http://www.opensecrets.org/news/2012/10/2012-election-spendi...