This already happens in judge elections in many states. Certain "business-friendly" candidates are showered in campaign money, with the expectations that when certain cases are appealed those judges will end up making "the right choice".
I've had this idea for a while already. Indeed, it would be interesting to set up a free market system for the governments. US seems to be an ideal place for this sort of experiment given the ease of movement. Competition between states could be quite healthy.
One relatively easy change that would almost completely remove the quid pro quo bribery effect of campaign contributions is to anonymize contributions so that candidates never know who their contributions are coming from. That way there would be no payback possible, and influence peddling through campaign contributions would become a thing of the past.
Candidates expresses their opinion on X; those with a vested interest in X pour tons of money into his campaign so that the candidate that they agree with is selected. And since that candidate already shares the position with them, when he needs backing from industry that's who he'll meet with.
Anonymizing campaign contributions wouldn't have an effect on political speech and it wouldn't have an effect on who you gave money to. (You'd still be free to say who you contributed to. You'd also be free to lie about who you donated to.) It would only change the way the money was handled, with the ultimate effect of removing the quid pro quo from donations.
It's not bribery to try and support someone whose views you agree with, or to have experts available to answer questions on complicated issues. Remember, campaign contributions don't give them a house, or boats, or planes, etc.
And by corporation I don't just mean GE etc, I'm thinking of any group of people who have a shared ideology and are working to influence policy.
And with campaign contributions? Come on. For the federal elections of 2008, we used $5.3 Billion dollars. What did we get for it? The exact same number of elected officials we would have if we spent $0.
What value was created? Better representatives? Quality entertainment?
What else could that money have been used for? As I said earlier: Ugh.
If lobbyist money can affect government policy - and it can - then it is always a worthwhile investment for those who have money to invest.
Basically, decentralizing government is, surprisingly enough, not a magic bullet.