Barreling toward a noon vote that could reopen the government, Republicans say they have an offer Democrats shouldn’t be able to refuse.

The proposal: an amended three-week short-term spending bill (one week shorter than the original bill that failed last Friday) that funds the Children’s Health Insurance Programs for six years, and an assurance from Senate Republican leaders that an immigration bill will see a debate and a vote in the coming weeks.

But as of Sunday night, Democrats were still saying “no deal.”

As the government shutdown enters its first workweek day, the impasse in the Senate comes down to a deepening frustration over the state of immigration negotiations and longer-term budget talks. Republicans have punted on finding a legislative fix for the Obama-era Deferred Action for Childhood Arrivals program since September, when the Trump administration announced it would end the program by March 5. They’ve also kicked budget negotiations down the road, instead passing three short-term spending deals since October 1.

But at this point in negotiations, it’s become difficult to parse what’s still in contention. At the beginning of shutdown talks, Democrats said they wanted to increase the urgency of immigration negotiations and ensure a vote on a final bipartisan agreement. Republicans have heeded part of their demands.

There are still three crucial factors in these negotiations that are giving Democrats pause and holding up a final deal to open the government. Here’s what’s still up in the air.

1) When is the vote on an immigration bill?

Senate Democrats and their Republican allies, first and foremost, want a guarantee on when Senate Majority Leader Mitch McConnell will move an immigration plan. The Republican leader has so far proven elusive in the DACA debate, famously promising to Sen. Jeff Flake (R-AZ) a vote by the end of January, a pledge that looks unlikely to be kept.

On the Senate floor Sunday night, while proposing to keep the government open through February 8, McConnell gave some idea of what he was willing to guarantee.

“Should these issues not be resolved by the time the funding bill before us expires on February 8, 2018, assuming the government remains open,” he said on Sunday, “it would be my intention to proceed to legislation that would address DACA, border security, and other issues.”

McConnell appears to be saying that come February 8, so long as Democrats don’t shutter the government again, he would bring an immigration bill to the Senate floor.

But there are still a lot of details to work out. Democrats might only agree to another short-term spending bill after February 8 — for another two weeks, for example — in order to keep the pressure on McConnell to honor his promise. Some Democrats have said that they would prefer a guarantee that the immigration bill come up before the end of this February 8 spending bill.

The point is, the process here will be important. Democrats want assurances that McConnell will bring up an immigration bill in the next few weeks — and they want to be sure that they have leverage to force the Republican leader to keep his word.

2) What immigration bill are they voting on?

Then the question becomes: Which immigration bill would McConnell bring to the Senate floor?

Sens. Lindsey Graham (R-SC), Dick Durbin (D-IL), and Flake have been negotiating an immigration deal for some time. But President Trump slammed that plan in the now notorious “shithole” meeting, and Republican hardliners in the House and Senate will be wary of anything that Graham, Flake, and Durbin — all doves — come up with.

“We had an election in 2016. Immigration was a major issue there. The American people, and especially Republican primary voters, made it clear that they wanted Donald Trump’s vision of immigration policy, not Lindsey Graham’s,” Sen. Tom Cotton (R-AR), one of those hawks close to the president, told reporters Friday.

As a backup plan of sorts, the No. 2 Democratic and Republican leaders in both chambers — Durbin, Sen. John Cornyn (R-TX), House Majority Leader Kevin McCarthy (R-CA), and House Minority Whip Steny Hoyer (D-MD) — have also been meeting to work on an alternative immigration plan. They have yet to present any details on their proposal and how it might resemble or differ from Graham-Durbin.

Reports indicate that Republicans, bolstered by Trump’s Department of Homeland Security, are pushing for changes to asylum law and the treatment of unaccompanied minors at the US border in the name of closing “enforcement loopholes” — policy changes that Republicans consider part of border security but that Democrats balk at as beyond what leaders agreed to focus on in a televised Oval Office meeting in early January.

There is also, in the House, a conservative hardliner proposal led by Rep. Bob Goodlatte (R-VA) in the mix. House Republican leaders have made their own pledges to the archconservative House Freedom Caucus that the Goodlatte bill would continue to be considered. This right-wing plan would criminalize all unauthorized immigrants in the US and curb legal immigration by 25 percent, while giving legal status — but not green cards — to current DACA recipients.

Which approach Congress takes on immigration sets the foundation for whatever the House and especially the Senate will work off, even if the bill goes through an amendment process. The Graham-Durbin plan likely has broad support in the Senate but might be a nonstarter in the House. The Goodlatte proposal has the opposite problem — if it can even get out of the House at all.

For now, Senate Republican leaders aren’t committing either way. “It’s not determined,” Cornyn told reporters Sunday night.

3) Are the White House and House Republicans on board?

But at the end of the day, Democrats don’t only want assurances from McConnell. They want to know that whichever immigration bill is finally given a vote, and passed, in the Senate will then make it to the president’s desk.

Democrats have reason to question McConnell’s assurances. After all, they saw this scenario play out in 2013, when Republican Speaker John Boehner refused to bring a Senate immigration bill up for a vote in the House, saying it wouldn’t receive the support of the “majority of the majority” party.

So Democrats are calling to attach an immigration bill to some kind of must-pass spending or budget bill to ensure that it gets a vote in the lower chamber and sees Trump’s signature.

“We have to have in our own mind some way to ensure that the House feels a need to bring up the issue as well,” Durbin told reporters.

But while McConnell has agreed to allow for a vote on immigration in the Senate, he has been unable — or unwilling — to bind the House and Trump in that process.

“Mitch can’t tell what the House what to do, and can’t tell the president what to do, but we can tell ourselves what to do,” Graham, who says he is “comfortable” with McConnell’s assurances, said. “When Democrats say that we gotta get a commitment from the speaker of the House and president, that’s outside his lane.”

The politics of immigration negotiations get complicated between Trump and the House. House Speaker Paul Ryan has made several promises to the most conservative faction of his conference, including to have a vote on the right-wing Goodlatte bill and an assurance that he wouldn’t allow a vote on an immigration bill without the “majority of the majority.”

It’s made Senate Democrats uneasy. Meanwhile, Trump, who continues to engage immigration hawks in negotiations, has assured Congress’s hardliners — like Rep. Mark Meadows (R-NC) and Sen. Cotton — that he wouldn’t approve of an immigration bill without their blessing. No proposal put forward by Meadows and Cotton has received bipartisan support.

Ryan hasn’t been directly involved in Senate negotiations, but Cornyn says he’s been kept in the loop.

“They’re an independent body; they’ll do what they want to do,” Cornyn said. “But I’ve kept the majority leader advised of what’s going on, so he knows what’s happening.”