Where does campaign cash go?

There's much discussion about how money corrupts politics, and on the need for campaign finance reform. I don't see the difference between a campaign contribution and a bribe. Perhaps that's just me, but here's the question no one ever asks:

Where does the campaign cash go once it is given to the politico?

Do you really think balloons, campaign posters, and even 30 second T.V. spots are that expensive? Enough to corrupt an entire American system of government? So the money goes to the politico, and the politico spends it on Madison Avenue? The T.V. networks and Ruppert Murdoch? Is that really where the true power lies?