It's not a matter of simply accepting corporate contributions. It's a matter of what's done in return for those contributions and the non-arms length relationship between many politicians and corporations.
All I have heard was that he accepted 5k from Merck.
There is no proof of anything else.
Every politician is vunerable on the issue, if they have ever had to run for re-election. You are going to get money from people who like what you did. You are going to do things that make people who gave you money happy.
It’s just a fact of life. McCain tried to fix this by his campaign finance reform. I don’t want to go down that route again. Overturning Citizen’s united would help, but I don’t want to do that either.
You play with fire if you are a politician and attack others over “appearance” with no evidence of anything untoward. Every politician, including Palin and Bachmann, have received money from people who are presidents of companies that made money based on their votes. If Bachmann voted for tax cuts, they helped everybody who pays taxes. Palin pushed more drilling, and took money from companies who are in the drilling business. As someone else pointed out, she raised taxes on oil companies for taking a state resource, but not the fishing industry.
None of these are improper, but all could be made to look improper by a media looking to tear us down.