First, a bit of background: The core of a gun deal isn't the assault weapons ban. That will get a vote on the Senate floor, but it won't pass, and it's long been clear that it won't pass. A ban on assault weapons also isn't, as a policy matter, the most important piece of a gun-control package.

That designation goes to universal background checks.

(Mel Evans / The Associated Press)

Right now, if you go into a Wal-Mart, or a Joe's Gun Shack or any other federally licensed firearms dealer, and try to buy a gun, they run you through a background check, and then they keep a record of that background check in a folder. It's no big deal.

But a lot of gun purchases -- some say as many as 40 percent, though there's reason to doubt that figure -- don't run through federally licensed dealers. They're private transactions at gun shows or between neighbors. Most of these sales are perfectly harmless. But they're also a target for people who want guns -- sometimes lots of them -- fast, and can't afford to have many questions asked.

That's where things get a bit dangerous. As Wonkblog's Brad Plumer reported, "by the late 1980s, surveys from the Bureau of Justice Statistics found that some 80 percent of those who used guns in crimes bought their weapons from the secondary market."

The idea behind universal background checks is to extend the exact same process used when you buy a gun in Wal-Mart to all gun transactions. So, gun shows would now have a booth that does background checks. Private sales between two friends, or two people who decided to make a deal on a message board, would require the buyer to complete an online background check. Background checks for everyone!

Democratic Sen. Chuck Schumer and Republican Sen. Tom Coburn have been negotiating this issue, and on most of it they've very, very close to a deal. But there's one sticking point: Record-keeping. Schumer wants a record kept of the background check. Coburn won't agree to anything of the kind.

The case for record-keeping is twofold. The first argument is compliance. If we're not keeping records, how can we be sure anybody is complying? Coburn's argument is that federal agents can conduct stings in which they try to buy guns without completing a background check and then bust sellers who aren't following the rules. Schumer's office is skeptical that Congress will appropriate enough money for stings on the scale required to make this work.

The second argument is that the records are needed so law enforcement can trace the history of guns that end up in crimes. "Sales records are required for trace data," explains Susan Ginsburg, who served as senior adviser for firearms policy coordination during the Clinton Administration. Without it, "you lose the ability to trace the firearm past the first seller." California forces the collection of this data, and there's solid research showing it's helped investigators trying to track the firearms used in crimes.

The argument against this kind of record-keeping appears to be a bit hazy. There's a principles-based claim, which is that gun ownership is a constitutional right and, therefore,  onerous burdens on law-abiding citizens are simply wrong. That's a bit hard to square with  the fact that most gun sales go through exactly this process today and that guns are perfectly easy to get.

Prominent Republicans will admit, off the record, that they're catering to fear and paranoia that the NRA has whipped up about the creation of a national gun registry that would, eventually, be used to take away everyone's guns -- or worse. Here's NRA chief Wayne LaPierre at CPAC:

Their check only includes good, law-abiding people. It's going to be people like you and me. That's who their check will be. That's what they're after -- the names of good, decent people all over this great country who happen to own a firearm, to go into a federal database for universal registration of every lawful gun-owner in America. That's their answer to criminal violence? Criminalize 100 million law-abiding gun-owners in a private transfer? Build a list of all the good people, as if that would somehow make us safer from violent criminals and homicidal maniacs?

That's their answer? Are they insane? What's the point of registering lawful gun-owners anyway? So newspapers can print those names and addresses for gangs and criminals to access? I mean, you know that's happened before.

Democrats protest that the government wouldn't be collecting any of this information, much less storing it. Instead, gun shops and private dealers would collect and keep this information, just as they do now -- the feds wouldn't access any of it unless they were investigating a crime.

But this gets to the real argument here, which is about votes. If Schumer is willing to drop the record-keeping provision, Coburn will join his bill, the NRA won't raise too much of a fuss, and the recordless background checks, which are still an improvement over the status quo, will pass. At the moment, Schumer is trying to find a way to pass the bill that permits record-keeping, perhaps with another Republican sponsor. But he hasn't found one yet.