Larry Lessig calls campaign fund-raising another form of corruption. It is interesting that in India if it were possible to get special interests to lawfully contribute to the campaign funds of politicians and not their own private accounts, we would probably declare victory against political corruption.
But, if you leave aside the fact that one is pernicious but lawful (the US) and the other is illegal and pernicious, there is little to choose between the two forms of corruption. The Indian version enriches the politician and his family. The primary use of that money is to fight elections (where the funds are used to buy mixer-grinders for the electorate, not TV ads). Money therefore becomes the means to stay in power.
In the US, it is the other way around. Campaign funds are used to fight elections. Once you win there are other legal ways to make money. Like through your spouses.
Ultimately, money and power are both means to ends and ends in of themselves. Whether special interests provide money to the politician or his campaign fund, they corrupt government and weaken democracy.