Is it illegal to tie campaign contributions to a specific policy goal?

Question

The petition Investigate Chris Dodd and the MPAA for bribery after he publicly admitted to bribing politicans to pass legislation implies that there is something illegal about this threat to withdraw campaign contributions to politicians:

"Those who count on quote 'Hollywood' for support need to understand that this industry is watching very carefully who's going to stand up for them when their job is at stake. Don't ask me to write a check for you when you think your job is at risk and then don't pay any attention to me when my job is at stake," This is an open admission of bribery and a threat designed to provoke a specific policy goal.

Surely lobbying is intended to promote one's goals; are there specific legal limitations to tying a campaign contribution to a political goal ("designed to provoke a specific policy goal")?

Answer 1

It is illegal to tie a contribution to a demand or to accept such a deal.

Under the Hobbs Act (DOJ summary), further clarified in Evans v. United States, an elected official cannot obtain a payment, solicited or not, in exchange for an official act. The payer must make it clear to the payee that the payment is in exchange for the official act. Subsequent actions don't bear on the legality.

From the other perspective it is illegal if it qualifies as Bribing a Public Official.

The recent legal trouble of Jack Abramoff is extremely relevant and points out the gap between the law and its enforcement.

Edit: I was pretty focused on the title question and forgot that in the text of your question you focus on a petition making a specific claim. I'm not trying to answer if that specific claim is legal or illegal.