Negotiations in Congress over the fate of the nearly 700,000 unauthorized immigrants who are losing their deportation protections and work permits as the Deferred Action for Childhood Arrivals program ends are beginning to seem like an oddity of physics.

The closed-door talks among a handful of senators (led by Sens. Dick Durbin (D-IL), Lindsey Graham (R-SC), and Jeff Flake (R-AZ)) haven’t fallen apart — yet. But they’re moving at an impossibly slow rate. After months of discussion, no one has yet put forward a bipartisan bill or even a framework, so it’s difficult to see how they’re still moving forward.

Meanwhile, in public, the stances that the White House, Republican congressional leaders, and Democrats have taken appear irreconcilable. And Trump’s own statements have been all over the map.

Democrats are doing nothing for DACA - just interested in politics. DACA activists and Hispanics will go hard against Dems, will start “falling in love” with Republicans and their President! We are about RESULTS. — Donald J. Trump (@realDonaldTrump) January 2, 2018

Congress has twice asked the White House what its hard-and-fast demands are on a DACA deal, and on both occasions — in October and again on Friday — the White House’s response has been a wish list constituting a comprehensive crackdown on legal and unauthorized immigration. Last week, two Republican senators accused Democrats of being unwilling to make even moderate concessions on border security.

The public disagreements about policy are to some extent a mirage. On Monday, two House members offered up yet another bipartisan DACA bill — the fifth, by Vox reporter Tara Golshan’s count, that offers some vehicle to help DREAMers. If the DACA negotiations fall apart, it’s more likely to be because of disagreements about the idea of a compromise itself, or process disputes, than over the policy specifics. (And yes, that includes “the wall.”)

That said, there are a lot of ways the talks could break down — which means, in Congress, they probably will.

Here are seven things, ranked by likelihood, that could kill a DACA deal.

1) Republicans decide they don’t want it badly enough

At a certain point, someone is going to need to produce, in public, an actual policy framework that could provide the basis of a DACA deal. There will need to be something that Congress can vote on and the president can sign.

And since Republicans can’t pass anything without Democratic votes in the Senate (they have 51 votes, and need 60 to overcome a filibuster) coming out only with DACA proposals that no Democrat would sign on to is tantamount to saying that they don’t actually care about a DACA fix all that much.

But it’s still not clear that either the White House or Republican congressional leadership is interested in cutting a bipartisan deal.

In December, the Senate’s bipartisan working group asked White House Chief of Staff John Kelly to tell them what the administration would need in a DACA deal for the president to sign it.

Late last week, they ostensibly got their reply: The White House sent the exact same document it had released in October, outlining an immigration “framework” that posited an overhaul of asylum laws, stepped-up interior enforcement, and a broad crackdown on legal immigration on the scale of the Trump-endorsed RAISE Act. Alongside it was a document outlining a “vision” for Trump’s border wall: 700 miles, at a cost of $18 billion.

Of course, the entire reason the senators asked Kelly for the White House’s demands in December was that they hadn’t taken the October wish list seriously. So the White House was essentially — as Breitbart correctly pointed out — thumbing its nose at the idea of a bipartisan DACA deal.

But what made the White House’s response particularly weird was that on Thursday, staff members had met with Senate Judiciary Committee Republicans — including Graham and Flake — and struck a preliminary “deal” on DACA that they would show to Democrats as early as Tuesday.

The bottom line appears to be that the White House hasn’t decided it does want a deal, and pushed staff to adhere to the party line. Neither have congressional Republicans: In the House, a group of relatively conservative Republicans has started their own set of DACA “discussions,” which is unlikely to result in a bill that can get Democratic votes or pass the Senate.

While it’s unfair to compare the majority party to the minority party on this, it’s worth noting that Democrats, especially in the Senate, appear to be deferring to the working group and prepared to support whatever comes out of it.

That doesn’t mean that the Republicans who do care about making a deal — or those who just want to avoid getting blamed when hundreds of DACA recipients a day start losing their protections when the program’s official sunset date hits in March — won’t ultimately prevail. It just means a lack of Republican will is the biggest threat right now.

2) Disagreement over attaching a DACA deal to a must-pass bill

Republican congressional leadership is pretty adamant that a DACA deal shouldn’t be attached to a government spending bill, like, for example, the one they need to pass by January 19 to keep the government open.

Democrats in Congress are equally adamant that a standalone immigration bill that would legalize some unauthorized immigrants will never pass Congress — especially the House, where it would be subject to the unspoken “Hastert Rule” that bills can only be brought to the floor with the support of a majority of the Republican caucus.

Depending on how the next two weeks shake out, this impasse could lead either party to walk away from DACA talks. If Republicans try to punt the January 19 deadline with another two-week continuing resolution (as they did twice in December), Democrats might refuse to go along — at which point, Republicans could pull out of the DACA talks by saying Democrats “poisoned the well.”

Alternatively, if Republicans simply refuse to attach a DACA deal to a spending package, Democrats could stop trying to work with them on DACA, since they wouldn’t want to negotiate on a bill that would never pass anyway.

This is a classic “each side blames the other” situation. Republicans would complain that Democrats simply weren’t willing to go through the legislative process the right way; Democrats would retort that they couldn’t guarantee a bill would even go to the floor if it wasn’t attached to a “must-pass” bill; Republicans would point to McConnell’s promise to bring a standalone immigration bill to the floor in January; Democrats would counter with the promises Republicans made to get Susan Collins’s vote on the tax bill, then broke within the week.

The only reason this isn’t the most likely obstacle to a DACA deal is that the deal would have to make it to the “agreed-upon policy framework” level first, and, per point 1, it’s not clear they want to go that far.

3) Negotiators can’t agree on anything they can call a limit on “chain migration”

For the most part, the policy on a DACA deal is the easy part. The biggest obstacle, policy-wise, is how to satisfy the demand President Donald Trump has begun to express regularly that any deal on DACA “end chain migration.”

The demand is hard to satisfy partly because it’s not clear what exactly the Trump administration is asking for — the president’s sloppy use of “chain migration” implicates all family-based immigration, and the proposal he’s endorsed to “end” it, the RAISE Act, would slash legal immigration to the United States in half.

It’s also a demand that’s emerged as important only in the past few weeks (months into the DACA negotiations), and one that can’t be solved just by throwing money at the problem, which is Congress’s preferred way to address specific legislative demands.

But to get a bill the president will sign, negotiators have to take the demand seriously.

Senators appear to be interpreting the “chain migration” demand to mean that the people who are legalized under the deal — DACA recipients and those who would have qualified for the program — will be restricted in their ability to sponsor their relatives for legal immigration to the US.

There’s some disagreement about whether these restrictions would apply when the legalized immigrants were green card holders — who are already restricted in sponsoring family members — or after they were citizens. (There are concerns, and not just from Democrats, that a bill that discriminated against citizens in family sponsorship wouldn’t survive a court challenge.)

But in practice, this probably wouldn’t do a ton to restrict long-term immigration to the US: Many people who would be legalized under any DACA fix have siblings who are US-born, who will be able to sponsor their parents for citizenship when they turn 21 years old.

But there’s also some discussion of a more aggressive move to curb “chain migration,” targeting family visas for adult children and siblings of US citizens. These are already the lowest priorities in the immigration system, and most applicants have to wait years to get approved, but they’re also the most likely to create “chains.”

If Republicans want to eliminate those categories entirely (depending on how they want to do it), Democrats — especially those members who represent Asian-American communities — may well refuse. It’s something they might be willing to do in exchange for legalizing most or all of the 11 million unauthorized immigrants currently in the US, but not for only the DREAMers — a population who, after all, Republicans claim they want to find a solution for as well.

4) A diversity visa lottery dustup

Eliminating the diversity visa, a program in which immigrants from countries that don’t send many immigrants to the US are selected by lottery and subsequently screened, is another demand the president has lit upon in recent weeks as a DACA condition — particularly since an attack in New York City by someone who came to the US on this type of visa. But it’s easier to see Democrats agreeing to go along with it, depending on what’s erected in its place.

Democrats probably won’t agree to get rid of the visa lottery if those visas are simply eliminated, to result in less legal immigration overall. They might be willing to agree to reallocate the 50,000 visas issued a year by the lottery to other categories of immigrants — including, possibly, as a way to allow immigrants currently in the US on Temporary Protected Status (who can’t get green cards) to stay permanently, instead of lobbying the government to keep renewing TPS. And they could support a deal that would eliminate the “lottery” component of the diversity visa but allocate those visas to underrepresented countries by other means.

It’s possible that changes to the diversity visa won’t even end up in the final deal. It would be a complicated fix, and some members of both parties are wary of using the DACA deal to make unrelated changes to legal immigration. It’s not clear, meanwhile, whether anyone is insisting on diversity visa reform as the condition for their support — except for, possibly, the White House itself.

5) That darn wall

Every time it looks like DACA talks are hitting a snag, there’s temptation to blame the wall. That happened again last week: Reports characterized the White House’s requests to Congress as a “demand” of $18 billion in wall funding in exchange for a DACA deal, or as holding DREAMers “hostage” to get money for the wall.

But the Democratic aide who told Politico that the White House’s border vision was “far beyond the bounds of what any Democrat or Republican has been discussing” was correct. It’s not clear that Republicans in Congress are willing to spend $18 billion on a wall, much less that they’d demand it as a condition on DACA.

For that matter, it’s not even clear that the White House is making it a demand. The document was sent to Congress in response to a request from senators for the White House to articulate what it actually needed in a deal — but it was sent alongside the exact same “framework” the White House issued in October, which wasn’t taken as a serious starting point in negotiations at the time. And one of the people who first reported on the existence of the document, the Wall Street Journal’s Laura Meckler, specified that it was “not clear Trump [was] demanding [the] whole thing” in a DACA deal.

To the extent that the $18 billion document throws a wrench in DACA negotiations, it’s because it illustrates the first problem above: It’s not clear the White House is interested in making a deal that involves getting anything less than its entire immigration wish list.

Within Congress, the two parties seem much closer to each other than either does to the White House.

The numbers floated by two Republican senators, North Carolina’s Thom Tillis and Oklahoma’s James Lankford, on Thursday were much more modest: $1.6 billion to build 76 miles of border barriers. (Tillis and Lankford claimed even that wasn’t acceptable to Democrats, and that they’ve walked away from the Senate working group because of Democrats’ border demands — but other reports indicate that Tillis and Lankford were basically kicked out of the group, so it’s not clear whether they are characterizing that correctly.)

If the White House’s actual demands match Tillis and Lankford’s — or if it can be talked into demanding something closer to theirs — the hardest part will be the messaging: Trump will have to be able to claim it is a border wall, while Democrats claim it isn’t.

But given that the White House has been known to claim, when convenient, that any physical barrier on the border is a “wall,” this doesn’t seem that difficult. It’s still very hard to imagine that Democrats will pass on the opportunity to allow hundreds of thousands, or more, unauthorized immigrants to become citizens, if the alternative is splitting a linguistic hair over what exactly the meaning of “wall” is.

6) Republicans decide they want some new enforcement trade-off

So far in negotiations, Republican leadership has been unwilling to make any public distinctions between what they really need and what they’d like to have. So it’s possible that McConnell, or Ryan, or Trump could decide that some other immigration enforcement measure is a condition for their vote. Restrictions on asylum claims? Interior enforcement? Increasing mandatory minimums for illegal reentry? There are lots of options; it’s just not clear that any of them is all that important.

7) The actual part of a DACA deal dealing with DACA recipients

Past immigration debates have focused on the minutiae of how unauthorized immigrants would be able to apply for legal status, how many of them would be eligible, and what their ultimate status would be. This immigration debate really has not — perhaps because the entire reason to make a DACA deal would be to address the fact that an overwhelming majority of Americans think DREAMers should have legal status.

Members of Congress appear to be in agreement that they want to strike a balance between two DACA legalization bills already proposed:

1) The DREAM Act, co-sponsored by Democrats and a few Republicans

2) The SUCCEED Act, backed by more conservative Republicans

Those two bills aren’t all that far apart to begin with: They differ mostly in how long people would be in provisional status before being eligible to apply for green cards, and the SUCCEED Act has stricter eligibility requirements in some regards.

Any hybrid of the two would almost certainly allow more immigrants to legalize than were protected over DACA: It would apply not only to people who have DACA now or had it in the past, but also to those who would have qualified, or who are currently too young but would have qualified once they turned 15.

The only politician who’s expressed opinions about who should be legalized and how is Department of Homeland Security Secretary Kirstjen Nielsen, who told a reporter Tuesday that she didn’t think children should be eligible for legalization — a strange position, since most politicians are sympathetic to the idea of “DACA kids.” But Nielsen doesn’t even appear to be in the room for negotiations. And the president, who continues to promise excellent “results” for DACA recipients, is probably not going to pore over the legalization details of a bill sitting on his desk.