By popular demand, here is the Return on Investment chart from last night's show, revealing that the support of the NRA is not as powerful as the politicians in its thrall seem to think. The source for the data can be found on this page from the Sunlight Foundation. The information on the NRA specifically is here and paints an interesting picture. The organization did support 27 candidates who won, and opposed 6 candidates who lost, but less than 1% of their spending went to those races, indicating they were sure bets that didn't actually require an political influence from the NRA. In the races where they did try to throw their weight around, particularly the presidential race, their record is abysmal.
I notice they spent $472,909.58 opposing Sherrod Brown for Senate in Ohio but also spent $10,713.48 in his support. I'm not sure what the deal is there. Just covering bases?