It's one of the things I detest about politics in Italy: ordinary people are so convinced that nothing can ever change that they make zero effort to do anything, and, surprisingly, things do not change.
If campaign contributions were entirely banned I doubt it would make much difference, because legislators are too busy to pull information on every topic that they feel they need to Do Something about, and its the people with lobbyists who succeed in pushing out the (fraction of the) information needed.
http://maplight.org/us-congress/bill/112-hr-3261/1019110/tot...
By obvious, I mean in the game theory sense i.e a system of selfish rational humans acting under the rules of "democracy".
The U.S. system has some factors which make it worse e.g. "first past the post" voting leads to a two-party system from which the electorate cannot break out.