No, I do not think it works that way.
Goldman Sachs donated a pile of money to Obama, and yet Obama has charged Goldman Sachs with fraud. That does not sound like all that money bought them the influence they would like to have.
The banks contribute because what they think they are going to get.The candidates need the money, and since officially, they get it with no strings attached, they simply take it. Perhaps if Goldman Sachs phones Obama he will have his calls returned, and I'd get an e-mail from a secretary. But that does not guarantee favors.
Republicans hate regulations and taxes on general principles. Small government and lower taxes is most of their platform.