WASHINGTON — Senate Majority Whip Dick Durbin has been trying to grant young undocumented Dreamers a path to citizenship for two decades.
He believes he's closer than ever to success.
But it all hinges on an arcane procedural decision in the hands of the Senate parliamentarian, who will rule on whether certain changes to immigration law are eligible for the filibuster-proof budget process that Democrats are using to pass a multitrillion-dollar bill.
"I'm losing sleep over it," Durbin told NBC News. "It is the best opportunity we've had in 20 years."
Democrats want to allow four categories of people legally in the U.S. to apply for permanent residence: DACA beneficiaries, temporary protected status recipients, farm workers and essential workers.
Last Friday, Democrats presented their case to the parliamentarian behind closed doors for why this policy complies. It is unclear when the ruling will come, but Democrats are bracing for it as early as this week.
They have set aside more than $100 billion for immigration in the budget resolution. They argue it would have a direct impact on cost and revenue, due to the fees for the costly application process and the taxes the immigrants would pay. They cite precedent on making immigration changes in budget reconciliation, including one from 2005 on recapturing unused green cards.
Democratic staffers came away optimistic that they made a strong case, according to sources familiar with the meeting. But Durbin, an Illinois Democrat and chairman of the Judiciary Committee, has seen near-misses on immigration before.
"I don't know how she's going to rule," Durbin said. The precedents are "part of our argument," he added. "I don't know what's convincing."
The House has already begun moving its immigration legislation through committee.
Sen. Alex Padilla, D-Calif., said there is nervousness among immigration advocates and "justifiably so."
"We've seen people try and come up short time and time again," adding that this is a unique moment that creates a "need to get this done through reconciliation."
Republicans made the opposite case to the parliamentarian, arguing that immigration changes have nothing to do with tax or spending policy and should therefore be ruled ineligible.
"I hope she rules with us. This is not a budgetary matter, it's a major policy change," said Sen. Lindsey Graham of South Carolina, the top Republican on the Budget Committee. "And we'll see."
"If you give legalization without border security, you have another run on the border," he said. "That would be the end of bipartisan immigration reform for a long time."
Sen. John Cornyn, R-Texas, added: "This is a big, substantive law change. It's not going to be successful."
If the parliamentarian rules it out, Congress would have to pursue immigration legislation through the regular process, which requires 60 votes in the Senate to defeat a filibuster. That means winning at least 10 Republican votes, which is extremely unlikely on the legalization measures Democrats want.
Attempts under the last three presidents faltered, and the two parties moved further apart under former President Donald Trump — Democrats in a more pro-immigration direction, Republicans in an increasingly anti-immigration direction.
Immigration advocates see the reconciliation bill as the best — if not only — chance in the near future.
"This is the key moment. A lot of people who are living this personally — I wouldn't want to speak to the depths of their anxiety except to say it is tremendous," said Todd Schulte, the president of the pro-immigration group FWD.us. "This needs to happen via reconciliation in part because getting 10-plus Republicans and 50 or so Democrats is really, really, really challenging. And that's understating it."
"It's unfortunate that there's not bipartisan votes for this now," he said.
Senate Majority Leader Chuck Schumer, D-N.Y., said he's unsure when or how the parliamentarian will rule, but if she rules to allow immigration provisions, the party will have 50 votes for them.
"I believe our full caucus supports immigration reform, absolutely," he told reporters Tuesday.
Senate Minority Leader Mitch McConnell, R-Ky., said that "both sides agree" the parliamentarian is the "final word" on whether immigration or other provisions comply with the rules.
"Can't blame the other side for trying to use reconciliation as expansively as they want to," he told reporters on Tuesday. "That's always the temptation, the majority using the reconciliation process, but abiding by the ruling of the parliamentarian is essential to the functioning of the Senate."
Still, Democrats say they're willing to adjust the proposal to satisfy the parliamentarian, if need be.
"This is not a one shot deal, and we plan to pursue other options with her," Kerri Talbot, the deputy director of the advocacy group Immigration Hub, who worked on comprehensive immigration legislation in 2013 as lead counsel for Sen. Bob Menendez, D-N.J.