Updated 5:28 p.m. | The third branch of government has entered the immigration debate with a bang — with potentially profound impacts on President Barack Obama’s legacy, the lives of millions and the rest of this Congress.

The decision by a federal district judge in Texas late Monday to temporarily halt Obama’s executive actions on immigration could also give Republicans a way out of a shutdown showdown over funding for the Department of Homeland Security.

The standoff over the DHS appropriations bill has cast a chill over the start of this Congress, splitting newly empowered Republicans with no easy off-ramp — except, maybe, in the courthouse.

Democrats and the White House have had no incentive to cave on an issue they see as a political and policy slam dunk for their side, and one of the most sweeping actions of Obama’s second term.

Republicans still aren’t ready to cave either, with Speaker John A. Boehner of Ohio and Senate Majority Leader Mitch McConnell of Kentucky pressing Senate Democrats in the wake of the ruling to allow the GOP’s DHS funding bill to go forward.

But with Democrats pledging to once again block the bill next week, Republicans will now have to justify potentially shutting down parts of the Department of Homeland Security in an effort to stop a program that already is being blocked by the courts.

“It won’t change the vote Monday,” a senior Democratic aide said, adding that Democrats want to fund the DHS before having a debate with Republicans over immigration.

“The only difference is that now they have an off-ramp to get out of their political jam,” the aide said.

One House senior GOP aide acknowledged the ruling might make it easier to avoid a shutdown.

“The judge’s ruling should make a short term funding extension pill marginally easier to swallow,” the aide said. “Like most medicine, it was never a pill anyone actually wants to take, but at least now it wouldn’t taste as bad on its way down.”

Sen. Jeff Sessions, R-Ala., urged his fellow Republicans not to use the court case as an excuse to punt.

“We cannot and must not establish the precedent that we will fund illegal actions on the hope that another branch of government will intervene and strike down that illegal action at some later point,” he said in a statement.

Obama predicted his actions would ultimately be upheld.

“This is not the first time where a lower court judge has blocked something or attempted to block something that ultimately is going to be lawful and I’m confident that it is well within my authority,” he said, per a pool report.

Obama knocked Congress for “votes to kick out young people who have grown up here and who everybody recognizes are part of our community, and threats to defund the Department of Homeland Security. …”

“My strong advice right now to Congress is, if they are seriously concerned about immigration, about our borders, about being able to keep criminals out of this country, then what they should be doing is working together and working with the administration for a comprehensive immigration policy that allows us to be both a nation of laws and a nation of immigrants.”

The potential for a courtroom battle was clear when Obama announced his controversial executive action in November.

CQ Roll Call asked assembled senior administration officials at a background briefing ahead of the rollout about the possibility of a legal challenge. The officials expressed confidence they would prevail — doubting anyone would have standing to sue and insisting Obama’s decision had ample precedent as an exercise in prosecutorial discretion.

Many presidents have granted some significant level of executive amnesty on their watch, including President George Bush, they noted.

The Supreme Court has granted the government “nearly absolute prosecutorial discretion” in other cases, one official said. Prosecutorial discretion undergirds the decision to halt some deportations, but critics say there is little legal justification for the administration’s decision to issue work permits. White House officials contend the issuance of permits is well within the discretion of the Department of Homeland Security and note that Bush also gave immigrants work permits.

But Republicans have ripped the permits and the three-year stay on deportations on a daily basis, calling both moves unconstitutional and citing Obama’s own statements that he cannot change the law by himself.

A number of House and Senate Republicans already have filed an amicus brief backing the 26 states challenging the president’s actions.

The judge in Texas didn’t rule on the key constitutional questions at stake — that’s still to come. (It’s worth noting the DHS funding bill only runs through the Sept. 30 end of the fiscal year, making its immigration provisions moot if the judge’s order remains in effect and isn’t overturned on appeal.)

The impact was immediate.

Homeland Security Secretary Jeh Johnson put off plans to begin accepting applications for part of the program this week expanding DACA — Obama’s 2012 executive action aiding immigrants brought here as children. He also announced the department would not take applications for the broader program known as DAPA while the court’s order remains in effect.

He added that Homeland Security’s new enforcement guidelines prioritizing the deportations of criminals remain in effect. As a practical matter, that means most illegal immigrants who are not recent arrivals have little chance of being deported.

Attorney General Eric H. Holder Jr. said at the National Press Club that he expects the case “will be ultimately be decided by a higher court, if not the Supreme Court.”

In the end, it would only take five Republican nominees on the Supreme Court to agree with Republicans to reverse the president’s decision.

That potentially explosive case will unfold just as the race to replace Obama in 2016 heats up.

The issue of immigration, though, was always going to effectively be on the ballot in some form; Obama’s executive actions could have been reversed by a future president, if not by the courts or Congress.

Prospects for a legislative breakthrough in the meantime remain as bleak as ever.

Matt Fuller and Humberto Sanchez contributed to this report.

Related:

Reid Allies See Immigration Fight Helping Re-Election

Boehner: House Has Done Its Job to Fund DHS

White House Thinks GOP Will Blink on Immigration Action

Obama: Back Immigration Action Because of Christmas, Bible

Obama’s Own Words on Immigration Are Republicans’ Best Ammo

Obama Immigration Action Full Speed Ahead

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