There shouldn't be a ban on letting a corporation donate money to the candidate they support. They have a right to donate money and show who they are supporting. It is their freedom to choose who they support and how they do it. Instead of banning corporations maybe they should put a limit on how much a corporation can donate.
I does not really matter because they will find a way around it. Politicians always do. Just like with the ads now, some of them are sponsored by groups and not the candidate. You can not tell me that the candidate does not have some thing to do with the add that is put on TV.
What it does is, keeps corporations from buying off a candidate in secret, ensuring the integrity of the race does not come into question. If you allow corporate contributions during a political campaign, you will really be risking a total bought election. So I don't think banning corporate contributions during a campaign violates First Amendment rights, rather I think it keeps the campaigns honest or at least is intended to.
I do not believe that banning corporate contributions during a political campaign violates First Amendment rights because the Constitution was not written to protect the interests of corporations, but rather, individual citizens. Massive corporate contributions dwarf smaller contributions made by individuals, giving them far too much influence in national elections. Individuals within corporations would still be able to make personal contributions to the candidates of their choice.