From Ocala.com:

Manchin, a moderate Democrat, is an NRA member who aired a 2010 campaign ad in which he literally shot a hole through Democratic environmental legislation that he pledged to oppose.

Also involved is Sen. Tom Coburn, R-Okla., another NRA member with a strong conservative record but occasional maverick impulses; No. 3 Senate Democratic leader Charles Schumer of New York, a liberal; and moderate GOP Sen. Mark Kirk of Illinois.