That should not be news to anyone. The only thing that has recently changed is Citizens United makes it easier to just avoid having to pass through money through more middlemen to bribe politicians.

Before radio and TV, only the rich elite who had the time to research politics voted. After radio and TV, only the rich elite who had the money to buy election ad slots got representation.

It is illegal for corporations to donate money to politicians. 61% of raised funds come from individuals donating up to $2600 each. 23% come from PACs (which themselves may only raise money from individuals, not corporations), and the rest comes from self-funding and political party committees.

Edit: These numbers are from 2010 congressional elections. Also it's illegal for federal elections. State elections have their own rules.

Are the 23% from PACs money given directly to campaigns or does it also include independent expenditures?

Additionally, wouldn't it be better to look at expenditures in later elections such as the 2012 presidential election? Using the 2010 data is a bit biased because the Citizens United decision was only ruled on in 2010.

As for your point of donations being illegal for federal elections, it is true that direct donations are regulated, however outside "independent" spending by corporations is not illegal.

Additionally, Super PACs can accept unlimited contributions from corporations as long as they use the money for independent expenditures.