One way that opposition to the Civil War was suppressed was the denial of what right?

Question

and

What is set up to make political contributions to candidates for elected office?

Your answer could be states rights. Check this site for more information.
http://www.answers.com/topic/origins-of-the-american-civil-war

This site has the answer to your second question.

http://en.wikipedia.org/wiki/Political_action_committee