The bipartisan group of four Senators who are negotiating over a proposal to expand the gun background check system privately met this week to discuss where things stand, according to sources familiar with ongoing talks. One source tells me the four Senators are “95 percent of the way there.”

This isn’t to say that the last five percent can’t scuttle the emerging compromise. As one source put it, that remains the “hardest part.” But there is reason for optimism that the four Senators — Republicans Tom Coburn and Mark Kirk, and Democrats Chuck Schumer and Joe Manchin — may be able to bridge remaining differences.

Here’s where things stand, according to several sources. There is general agreement on the concept of expanding the background check to cover most private sales, and on the concept of improving state mental illness data-sharing with the feds — which is important, because it means the four more or less agree on the fundamental policy goal here. The four Senators are in discussions about exemptions — sales among family members — and about tweaking the way background checks are performed for private sales in certain rural areas. But sources say those are unlikely to be sticking points. The four Senators are discussing yet another possible exception designed to make the deal more palatable to gun rights lawmakers: Exempting those who have already obtained “conceal and carry” permits, the idea being they’ve already undergone a background check.

One thing that still needs to be resolved is how to ensure that an expanded background check does not create some kind of national gun registry — again, in order to mollify gun rights lawmakers. The law as currently configured explicitly forbids the creation of any such registry, and it requires that any data collected during a legal gun transfer be destroyed within 24 hours. Despite this, the four Senators are discussing ways to write in new legislative language that would add additional safeguards against any data collection.

“There is complete agreement, among Democrats and Republicans in the talks, that nothing will be by law or look in any way like a national gun registry,” says Jim Kessler, vice president at the centrist group Third Way, who has been briefed on ongoing discussions. Third Way recently put out a memo explaining why such a policy simply can’t produce any national registry.

To put it bluntly, the problem faced by Republicans inclined to support an expanded background check is that GOP lawmakers (such as Orrin Hatch and Mitch McConnell) who don’t want to support this policy continue to misrepresent it, falsely claiming it would create a national gun registry. Because this convinces a lot of folks on the right that such an outcome is possible, Republicans inclined to support the proposal face major blowback, and so the four lawmakers are debating ways to add the additional safeguards.

There is some additional debate over what should happen to receipts from gun sales, which are currently kept by gun stores. One idea being looked at is letting the gun buyers in rural areas keep the receipts.

The key point that everyone should understand is that Democrats and gun control groups very likely will accept the exemptions and safeguards that will probably end up in the bill. The main goal of Dems and the left is solely to expand the background check system to include virtually all private sales within the law’s current framework, which explicitly guards against the creation of any gun registry.

There is still plenty of time for this to fall apart; it’s a truism in Washington that the last few steps are always the hardest. But it’s encouraging that the four Senators negotiating this appear to be very much on common ground when it comes to the reality of what this measure would actually accomplish, and what it should accomplish.