The Senate parliamentarian has nixed Democrats' back-up plan for getting immigration reform into a sweeping spending bill, handing them a second setback.  

Democrats had pitched parliamentarian Elizabeth MacDonough on legalizing millions of undocumented immigrants by making a change to the date for when undocumented immigrants within the United States can apply to adjust their legal status. 

But MacDonough told Democrats that the option was a non-starter, according to a copy of the guidance obtained by The Hill. Democrats are pursuing other back-up plans with the Senate referee, according to a source familiar with Democrats' strategy. 

Changing the registry date is a "weighty policy change and our analysis of this issue is thus largely the same" as for Democrats' previous proposal to provide legal permanent resident status to some immigrants, MacDonough told Democrats in her guidance. 

"It's unfortunate. I disagree with her ... but we'll go to plan C," said Sen. Bob Menendez (D-N.J.).

Senate Judiciary Committee Chairman Dick Durbin (D-Ill.) said he was “disappointed” in the ruling and that it left them with “limited” options. 

“[But] it still involved legal permanent residency; we knew we still had a real challenge,” Durbin said about the push to get a change in the registry date. 

Democrats had initially pitched MacDonough on using their spending bill to provide 8 million green cards to immigrants in four groups: "Dreamers," who came to the U.S. illegally as children; temporary protected status (TPS) holders; agricultural workers and other essential workers. But she rejected that earlier this month, saying that it was "not appropriate" for reconciliation, the budget process Democrats are using to bypass the filibuster on their spending bill.  

Democrats then pitched to MacDonough a change to the registry date for certain undocumented immigrants and beneficiaries of humanitarian parole programs, essentially implementing a statute of limitations for past unauthorized entries. 

It currently allows undocumented immigrants who came to the United States before 1972 to apply for legal status.

According to an analysis by FWD.us, changing the registry date to 2010 — allowing any migrants who’ve been in the country since that date to apply for residency — would make around 6.7 million people eligible for legal permanent residency.

MacDonough's latest ruling immediately renewed calls from outside groups for Democrats to overrule her — something they could do with total unity from their 50 members plus Vice President Harris presiding over the Senate. Top Democrats, including Menendez and Durbin, have indicated that won't happen. 

“While unsurprising, the parliamentarian’s second recommendation is another deep disappointment. Parliamentarian MacDonough’s reasoning is clearly flawed, and thankfully, her suggestions can be ignored," said Ju Hong, the board chair for the National Korean American Service & Education Consortium.

Frank Sharry, the executive director of America's Voice, added that "it's up to elected officials, not unelected staff attorneys, to decide the fate and future of millions."

"We call on our Democratic champions to explore every option, from a new plan to legalize millions to ways to sidestep the Parliamentarian’s advisory opinion," he said. "Democrats are in the majority. They have the power to get this done."

Updated at 4:30 p.m.