When I first heard about Vote-auction.com, I was convinced that explicit vote-selling could change the face of American politics.
On reflection, I'm not sure it will make much difference. In the hypothetical future where votes are traded on the Internet, political parties will win elections by starting with a core coalition of "true believers" inspired by charismatic leadership and then using cash to buy enough votes to win. In the actual present, political parties win elections exactly the same way, except that they buy votes implicitly with promises of government largess instead of explcitly with cash. (e.g., "Vote for me and I'll give you a Head Start program, or a business subsidy, or a tariff protection.") Either way, success depends on holding that core coalition together. It's not at all clear that you'd change the outcome just by making the vote-buying more explicit.
Whatever the process, the simplest theory predicts that the winner will walk away with only a small reward. If the presidency is worth $15 billion and a candidate thinks he can win it by buying $10 billion worth of votes, he's likely to be surprised by an opponent who offers $11 billion. Then the other candidate will offer $12 billion and so on, until the winner pays almost $15 billion for a $15 billion prize. That would be true—according to the simple theory—in a world where votes are sold for cash, and the same theory says it should be true in the world we live in today, where votes are sold for subsidies and spending programs.
There are only two ways around the theory's prediction: 1) An exceptionally charismatic candidate might be able to buy votes at bargain prices; and 2) candidates can collude with their opponents. If Candidate A agrees with Candidate B to limit bids, one of them can win the $15 billion prize for $10 billion and the two can split the remaining $5 billion. The winning candidate might even get good press by labeling his collusive agreement a combination of "campaign-finance reform" and "bipartisanship."
In the hypothetical future where all votes are traded on the Internet, it's easy to see how bipartisan collusion would line the pockets of politicians at the expense of voters by holding down the price of votes. In the actual present, the same thing is true for essentially the same reason. Without collusion, politicians who enrich themselves can be "outbid" by opponents who offer to duplicate their policies while returning a little extra to the voters through tax cuts or spending. The bidding continues until all excess profits are competed away. Only bipartisanship can limit that process.
So, when George W. Bush boasts about his record of working closely with Democrats, he's really boasting about his role in a conspiracy against the public. If Bush weren't working so closely with the opposition, he'd have to compete by offering the voters a better deal. By closing off competition, he makes it possible for both leaders in both parties to preserve resources for themselves and other faithful insiders. That's why so many politicians retire rich.