I think the money needed to buy votes is a rather US specific problem and maybe not that hard to attack. As example - in Germany we have 2 laws for reducing the dependency of political parties on private sponsors. The first is that TV stations have to send a certain amount of political spots before elections for all acknowledged parties and the parties only have to pay the self-costs of the stations for that time (around 35% of the price for commercial advertisement). The second law is that parties that get above 0.5% or 1% (depending on the type of election) receive money for each received vote (up to certain limits to prevent that parties just take part in an election to make money from that). I don't say it's perfect and there is still a lot of financing going on beside that, but it shows that the fight at least isn't futile and that it is possible to reduce the dependencies on sponsors.