It's easy to forget amid the emotional testimony of former Rep. Gabrielle Giffords in front of a Senate panel on gun violence Wednesday that the likelihood of any sort of sweeping measure to limit gun rights passing Congress is small.

Former Arizona Rep. Gabby Giffords (left and her husband Mark Kelly testify at a Senate hearing on gun violence. AP photo)

The chances of the assault weapons ban legislation -- as introduced by Sen. Dianne Feinstein (D-Calif.) -- making it through a divided Senate and a Republican-controlled House are remote, although things like banning high capacity ammunition magazines and instituting universal background checks still seem politically plausible.

The fact that smaller-bore measures seem the most likely to succeed is in part (and, really, more than in part) to the National Rifle Association -- perhaps the most effective single-issue interest group operating in the nation's capitol these days.  That influence is due to the NRA's four million members -- a built-in grassroots lobbying force -- as well as to the organization's heavy spending to elect people who support their views and keep those who back them in office.

Below is a chart that breaks down where the NRA's political spending -- $32 million worth -- went in 2012.  The chart reinforces that direct contributions to candidates are almost never the key to an organization's influence. Rather, spending heavily ($18 million) via issue ads and other outside spending tends to be the way in which true power is exerted in Washington.