Linda Greenhouse on the Supreme Court and the law.

There has been plenty written about the National Rifle Association in recent days. But nothing that I’ve seen has focused on the gun lobby’s increasingly pernicious role in judicial confirmations. So here’s a little story.

Back in 2009, when President Obama chose Judge Sonia Sotomayor as his first Supreme Court nominee, the White House expected that her compelling personal story, sterling credentials, and experience both as a prosecutor and, for 17 years, as a federal judge would win broad bipartisan support for her nomination. There was, in fact, no plausible reason for any senator to vote against her.

The president’s hope was Senator Mitch McConnell’s fear. In order to shore up his caucus, the Senate Republican leader asked a favor of his friends at the National Rifle Association: oppose the Sotomayor nomination and, furthermore, “score” the confirmation vote. An interest group “scores” a vote when it adds the vote on a particular issue to the legislative scorecard it gives each member of Congress at the end of the session. In many states, an N.R.A. score of less than 100 for an incumbent facing re-election is big trouble.

Note that the N.R.A. had never before scored a judicial confirmation vote. Note also that Sonia Sotomayor had no record on the N.R.A.’s issues. (True, she voted with an appeals court panel to uphold New York State’s ban on nunchucks, a martial-arts weapon consisting of two sticks held together with a chain or rope, commonly used by gang members and muggers. The appeals court didn’t even reach the interesting issue of whether the Second Amendment guaranteed the right to keep and bear nunchucks, ruling instead that the amendment didn’t apply to the states – which, before the Supreme Court later ruled otherwise by a vote of 5 to 4, it didn’t.)

Never mind. The N.R.A. had all the reason it needed to oppose Sonia Sotomayor: maintenance of its symbiotic relationship with the Republican Party. Once it announced its opposition and its intention to score the vote, Republican support for the nominee melted away. Only seven Republicans voted for confirmation.

One senator, Lisa Murkowski of Alaska, said by way of explaining her “no” vote that her constituents had expressed “overwhelming concern” about Judge Sotomayor’s views on the Second Amendment. However, Senator Murkowski told the National Journal at the time, “I am a bit concerned that the N.R.A. weighed in and said they were going to score this.” She added, “I don’t think that was appropriate.”

The following year, after the N.R.A. opposed Elena Kagan for the Supreme Court and announced that “this vote matters and will be part of future candidate evaluations,” Republican support for another nominee without a record on gun issues shrank to five senators.

At least Supreme Court confirmation debates take place in the light of day. Members of the public can tune in and decide whether they are persuaded that Elena Kagan represents “a clear a present danger to the right to keep and bear arms,” to quote the N.R.A.’s statement of opposition to her nomination. (Justice Kagan had never owned or shot a gun, but since joining the court has taken lessons and gone hunting with Justice Antonin Scalia, pronouncing the experience “kind of fun.”)

But the N.R.A. has begun to involve itself in lower court nominations as well, where it can work its will in the shadows. It has effectively blocked President Obama’s nomination of Caitlin J. Halligan to a seat on the United States Court of Appeals for the District of Columbia Circuit that has been vacant since September 2005, when John G. Roberts Jr. moved to a courthouse up the street. The president has submitted the name of the superbly qualified Ms. Halligan to the Senate three times.

When the Democrats’ effort to break a Republican filibuster failed last year, Senator Murkowski was the only Republican to vote for cloture, perhaps liberated by the fact that she won her last election as a write-in candidate, thus freeing herself of party discipline – which in the Republicans’ case effectively means discipline by the N.R.A. In this year’s Republican Senate primary in Indiana, the N.R.A. spent $200,000 toward the successful effort to defeat the incumbent, Richard Lugar, attacking the six-term senator for, among other sins, having voted to confirm “both of Barack Obama’s anti-gun nominees to the U.S. Supreme Court.”

When I wrote a year ago about the fate of Caitlin Halligan’s appeals court nomination, I tried to puzzle out the basis for the opposition. Silly me, I thought it had something to do with Republicans not wanting a young (she had just turned 45), highly qualified judge sitting in the D.C. Circuit’s famous launch position (hello, John Roberts, Ruth Bader Ginsburg, Antonin Scalia, Clarence Thomas, Warren Burger . . .)

Now I realize it’s not about anything so sophisticated. It’s about the N.R.A., which announced its opposition days before the cloture vote last December. It was only the second time in the organization’s history that it had opposed a nomination at the non-Supreme Court level. (The first was Abner Mikva in 1979, a former member of Congress from Chicago who won confirmation and who later served as President Bill Clinton’s White House counsel.) In a previous job as New York State’s solicitor general, Ms. Halligan, a former Supreme Court law clerk who is now general counsel to the Manhattan district attorney, had represented the state in a lawsuit against gun manufacturers. So much for her.

So that’s my N.R.A. story. The question is what anyone can do about it. The N.R.A. has embedded itself so deeply into the culture of Republican politics that it would take a cataclysm to break the bonds of money and fear that keep Republican office holders captive to the gun lobby’s agenda.

Well, a cataclysm just occurred, a few dozen miles from my office at Yale Law School. (My late father-in-law was born on a farm in the Sandy Hook neighborhood of Newtown.) There will be legislative proposals, and members of the Senate and House will debate them, maybe even enact a few, and people back home can decide what they think. How to get a handle on the gun problem is not my point. Rather, I want to offer the judicial nomination story as a canary in the mine, a warning about the depths to which the power of the gun lobby has brought the political system.

My point is this: It is totally unacceptable for the N.R.A., desperate to hang on to its mission and its members after achieving its Second Amendment triumph at the Supreme Court four years ago, to be calling the tune on judicial nominations for an entire political party. Free the Republican caucus. Follow Lisa Murkowski’s lead. Recognize a naked power play for what it is. Voters who think they care about the crisis of gun violence in America are part of the problem, not the solution – they are enablers if they aren’t willing to help their elected representatives cast off the N.R.A.’s chains. Call for an end to the cowardly filibuster against Caitlin Halligan, whose nomination the president resubmitted in September. The next time a senator announces opposition to a judicial nominee, demand something other than incoherent mumbo-jumbo. Tell the senator to fill in the blank: “I oppose this nominee because ____.” If there’s an answer of substance, fine. That’s advise-and-consent democracy. But if, upon inspection, the real answer is “because the N.R.A. told me to,” we have a problem. Based on these last few years, I think we do.