Senate Parliamentarian Elizabeth MacDonough rejected Democrats’ third attempt to include immigration provisions in their sweeping social spending plan, dealing a potentially fatal blow to the party’s efforts to protect millions of undocumented immigrants for the first time in years.

The plan, included in the House version of the bill that passed Nov. 19, would have drawn on “parole in place” authorities to allow an estimated 6.5 million immigrants who have lived in the U.S. since January 2011 to apply for five-year work permits and relief from deportation.

Sen. Richard J. Durbin, D-Ill., said Thursday evening he was “disappointed” with the ruling, adding that “we’re considering what options remain.”

Democrats and Republicans presented their opposing arguments to MacDonough at a formal meeting Dec. 1 to go over the immigration provisions. They had hoped to pass the overall bill before Christmas, but acknowledged this week that timeline would likely slide to January.

According to a copy of the guidance obtained by CQ Roll Call, MacDonough reasoned that Democrats’ proposal included policy changes that would outweigh their budgetary impact, violating the so-called “Byrd rule” for the same reasons as two prior proposals Democrats submitted that would have put millions on a path to citizenship. 

“The proposed parole policy is not much different in its effect than the previous proposals we have considered,” she said. “These are substantial policy changes with lasting effects just like those we previously considered and outweigh the budgetary impact.”

The decision was slammed in a joint statement released by Durbin, Senate Majority Leader Charles E. Schumer, D-N.Y., and Sens. Bob Menendez, D-N.J., Alex Padilla, D-Calif., Catherine Cortez Masto, D-Nev., and Ben Ray Lujan, D-N.M.

“We strongly disagree with the Senate parliamentarian’s interpretation of our immigration proposal, and we will pursue every means to achieve a path to citizenship in the Build Back Better Act,” they said.

Shortly before the House passed the bill, the Congressional Budget Office released an estimate predicting the bill’s Judiciary Committee provisions, which primarily fund immigration protections, would increase “on-budget” deficits over the next 10 years by $121.7 billion — roughly $14 billion above the amount allotted for those measures. In the second decade, the immigration provisions would add another $311.9 billion to deficits. 

The House-passed measure would also help immigrants, mostly from India, stuck waiting in a yearslong green card backlog created by strict per-country visa caps, by “recapturing” visas that went unused at the end of each fiscal year since 1992. But those provisions were not addressed in MacDonough’s decision Thursday.

Democrats had sought for months to pass major immigration changes through budget reconciliation, a process that allows bills to pass with a simple majority provided they are strictly budgetary in nature. 

Republicans, meanwhile, had long argued that immigration policy was beyond the scope of reconciliation bills.

“This guidance confirms, once again, what everyone already knew — that giving amnesty to millions of illegal immigrants isn’t a budgetary matter appropriate for reconciliation,” Sen. Charles E. Grassley, R-Iowa, ranking member of the Senate Budget Committee, said in a statement Thursday.

MacDonough’s ruling will likely escalate calls from Democrats to overrule her advice when the bill is considered on the Senate floor, a process that would demand widespread consensus among Democrats. 

House lawmakers have already called for senators to disregard MacDonough’s ruling; in November, dozens urged Senate leaders to prioritize immigration protections, even if it requires overruling MacDonough. 

“We cannot let an unelected advisor determine which promises we fulfill and which we do not, especially when the vast majority of Americans — in both parties — want us to provide a pathway to citizenship,” the lawmakers wrote.   

Following reports of MacDonough’s latest decision, Marielena Hincapié, executive director of the National Immigration Law Center and former co-chair of the Biden-Sanders unity taskforce on immigration, called on Senate Democrats to ignore MacDonough’s decision and pass language creating a path to citizenship.

“The path before us could not be clearer. Senate Democrats must use their power under existing Senate rules to disregard the parliamentarian’s advisory opinion and enact the permanent protections immigrants have fought for and deserve,” she said in a statement.

Several senators have also signaled openness to the possibility. Padilla has said repeatedly that “all options are on the table” when it comes to enshrining immigrant rights into law.

But it is far from clear whether moderates, specifically Sen. Joe Manchin III, D-W.Va., and Sen. Kyrsten Sinema, D-Ariz., would back such a move.

The failed effort could be Democrats’ last chance for years to make major changes to the immigration system. The party risks losing one or both chambers in the 2022 midterm elections, and Republicans have been largely uninterested in bipartisan immigration legislation amid a period of historically high crossings at the U.S.-Mexico border.