The folks on a panel charged with hashing out rules for the Every Student Succeeds Act say they really, really want to reach an agreement on testing and school funding regulations for the new law should look like.

But, as anyone who attended the eye-glazing negotiated rulemaking sessions this month and last month would tell you, agreement is looking pretty elusive when it comes to writing rules for “supplement not supplant.” (That’s the in-the-weeds funding provision that was the subject of a very wonky—but testy—back and forth between Education Secretary John B. King, Jr. and Sen. Lamar Alexander, R-Tenn., at hearing last week)

We’ll see how things play out over the final neg reg session, happening Monday and Tuesday. But just in case negotiators aren’t able to come to kumbaya, here’s a breakdown of how negotiated rulemaking (or “neg reg”, as the cool kids call it, fails) and what happens if/when it does:

How do you know if there is or isn’t an agreement? Right now, negotiators are looking at two broad buckets of regulations in ESSA. One is supplement-not-supplant, which calls for districts to make sure that federal funds are an extra and not a replacement for state and local spending.

The other is assessments, which covers a whole host of issues centered on testing, including how substituting a nationally recognized high school test for the state exam should work, when states can offer eighth graders an advanced math exam instead of the state test, how computer adaptive assessments should work, and what ground rules should be in place testing for special populations of students, including students in special education and English language learners.

Negotiators can reach agreement either on the broad bucket of “assessment” or on “supplement-not-supplant”, or both. Or neither.

But, importantly, in order to reach agreement on the broad category assessment, they have to agree on all of the regs for all the different topics. They can’t form a separate agreement on say, computer adaptive assessment, but not tests for students in special education. It’s the whole assessment enchilada or nada.

What are the next steps, should the committee fail to reach agreement? The department gets to write its own draft rules on assessment and/or supplement not supplant. The education community gets a chance to comment on those rules, then the department makes changes if it wants to and then finalizes the regulation. So basically, the usual process everyone is used to.

But wait! I sat through all those sessions, or read through some pretty long and wonky blog posts, so I know there’s been consensus on a few issues! Plus, there may be more agreement to come, even if negotiators can’t figure out everything. What happens to all that work if neg reg fails?. It’s up to the department. They could stick with the draft rules submitted to the committee as a proposal and include the agreed upon tweaks, or go in another direction. But it’s important to underline that the feds aren’t obligated to incorporate any agreements reached on smaller issues. So if the negotiators fail to reach a consensus on assessments overall, but they come up with a definition of say, nationally recognized test that they all agree to, the department doesn’t necessarily have to use that agreed on definition in whatever regs they eventually write. To be sure, they can put in language the committee agreed on, and it would probably be smart politics if they did, but there’s nothing that says they have to.

What about Congress? Do they get a say? Sort of. ESSA includes a twist to the regulating process that no other version of the Elementary and Secondary Education Act has had. If neg reg fails, Congress gets fifteen days to review regulations on the topics that were supposed to be negotiated before those regulations become final.

It’s true that lawmakers might have limited opportunities to change regs they don’t like during that period. But a Senate GOP aide told me back in December that congressional review of some regulations could “change the whole thought process of regulators--the ‘better to ask forgiveness than permission’ card isn’t really an option, and that’s pretty big when it comes to sneaky regulators,” the aide said at the time. If nothing else, the extra time gives lawmakers a chance to prepare a response to rules they don’t like.

Can a lawmaker overturn regulations? This question is worth asking, given Alexander’s criticism of the supplement-not-supplant regs. The answer is no, one lawmaker, working all by themselves can’t overturn a reg. But Congress could pass new legislation or an appropriations rider, to put a stop to a reg they don’t like. (This happened with the School Improvement Grant program regs.) They could also encourage the education committee to sue to get the reg changed, as Alexander did last week.

How big of a deal is it for states and districts if neg reg fails? Putting the policy aside for a second, a long delay in regulations could be bad news indeed, a district advocate said. Districts want to get certainty on regulations as soon as possible, said Noelle Ellerson, the associate executive director for policy and advocacy at the School Administrators Association “With accountability workbooks due in late spring 2017, the later any regulations come out, the harder it will be for states and districts to plan appropriately for the 2017-18 school year, and it increases the odds that some plans will still be under consideration as the school year starts,” she said in an email.

Tony Evers, who is representing state chiefs on the panel, told me in an interview last week that he’s hoping the negotiating process succeeds, in part so that he and his colleagues can get some certainty sooner rather than later.

But generally, states are already moving forward in reaching out to their local education communities to figure out what their new ESSA plans should look like and a delay won’t stop that process, advocates for state policymakers said.

Want more? The department has its own FAQ on this issue here.