Any good political fight needs a bad guy, and for liberals upset about congressional resistance to gun control legislation, the National Rifle Association is the bad guy of choice. And it's not a bad choice by any means. The NRA really does carry enormous clout on Capitol Hill.

But liberals — like Igor Volsky from ThinkProgress in this video — often like to express this clout in terms of the NRA's campaign contributions.

This is wrong. Money matters in politics, and the NRA does have money. But lots of lobbying groups have more money than the NRA and almost none of their clout. The NRA's true sources of power are twofold — people and focus.

Money only explains so much

According to Open Secrets, the NRA spent $11,159,167 on the 2012 election cycle, making it one of the biggest spenders on that election.

But the League of Conservative Voters spent almost as much ($10.8 million), and the large labor unions SEIU ($13.7 million) and AFSCME ($12.4 million) both spent more. These are all, as you would expect, big and influential groups. When labor unions came out swinging hard against Trade Promotion Authority this year, most Democrats in Congress lined up behind them. But the NRA is far more popular than that. A sizable minority of Democrats — including the president of the United States — broke with labor over Trade Adjustment Assistance, and at the end of the day it passed.

Republicans, by contrast, essentially march in lockstep with the NRA, and red-state Democrats fear its wrath. Money alone doesn't convey that kind of power, especially when the gun control cause can now put Michael Bloomberg's money in the field to counter NRA cash in cases where gun control is a high-profile issue in the campaign.

People and focus are much rarer than money

What the NRA has that relatively few other DC interest groups have is a genuine mass membership. The NRA's 5 million members give it ground troops who mobilize to call congressional offices, volunteer in campaigns, and share political views with friends and neighbors. The mere fact that a person would bother to have voluntarily joined a political advocacy organization sends a powerful signal to politicians that he or she is an engaged member of the electorate who will pay attention to political events and show up on Election Day.

This membership is made all the more valuable by the fact that the NRA is focused.

Most other advocacy groups with broad membership serve a wider range of purposes. The American Federation of Teachers has 1.6 million members, but those members didn't necessarily join the union because they agree with AFT about a particular policy agenda. Labor unions do lots of things that aren't political advocacy, after all, and they advocate on a wide range of issues. That means that on any given issue, union leaders can only realistically tap so much of their membership clout and that politicians know they don't need to agree with the union leadership on everything to be seen broadly as a good guy.

But the NRA really only does one thing: It opposes gun regulations. So when NRA leaders show up in Congress or in a state legislature with members behind them, people know the members are serious. And that even if politicians manage to cook up a gun bill or seven that does well in polls or focus groups (and liberals have gotten pretty good at this), the leadership of the organization can credibly communicate back to its members that the bill is bad for gun rights and should be opposed.

There are lots of groups in Washington with money, some groups with mass membership, and a bunch of groups with narrow focus. But since there tends to be a trade-off between focus and breadth of membership, the NRA is almost unique in combining the two.

This is why the NRA’s scorecards are far more powerful than its political donations.