President Obama’s new immigration program was supposed to begin accepting applications Wednesday from thousands of illegal immigrants hoping for relief from the threat of sudden deportation. Instead, the administration abruptly postponed the launch after a federal judge in Texas temporarily blocked the White House initiative.

In a decision late Monday, U.S. District Judge Andrew S. Hanen ruled that the deferred-deportation program should not move forward while a lawsuit filed by 26 states challenging it was being decided. Though Hanen did not rule on the constitutionality of Obama’s November immigration order, he said there was sufficient merit to warrant a suspension of the new program while the case goes forward. All told, Obama’s immigration actions are projected to benefit as many as 5 million immigrants, many of whom could receive work permits if they qualified.

The effects of Hanen’s procedural ruling rippled through Washington and underscored a broader challenge to the president as he seeks to solidify the legacy of his administration.

Along with the immigration action, the fate of two of Obama’s other signature initiatives — a landmark health-care law and a series of aggressive executive actions on climate change — now rests in the hands of federal judges. It is a daunting prospect for a president in the final two years of his tenure who believes he is on the path to leaving a lasting impact on in­trac­table and politically perilous issues, despite an often bitter relationship with Congress.

Now, Obama and his Republican antagonists in Congress face the uncertainty of having their disputes mediated by the third branch of government. In an appearance in the Oval Office on Tuesday, Obama said he was confident that he would prevail, telling reporters, “The law is on our side and history is on our side.”

President Obama says he disagrees with a Texas judge's ruling delaying his executive action on immigration. (Reuters)

“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,” he added, “and I’m confident that it is well within my authority” to execute this policy.

The immigration fight will probably head next to the U.S. Court of Appeals for the 5th Circuit after the White House vowed to quickly appeal Hanen’s ruling. In the meantime, Homeland Security Secretary Jeh Johnson said Tuesday that his agency would postpone plans to begin accepting applications for the new program, which would expand a 2012 program that defers deportations of immigrants who came to the United States illegally as children. (The 700,000 people who have already benefited from that program will not be affected by Hanen’s ruling.)

A second, much larger program designed to protect from deportation the undocumented parents of U.S. citizens and permanent legal residents was not scheduled to begin accepting applications until late May, and its future remains uncertain.

On health care, the Supreme Court will hear arguments next month in King v. Burwell, a case that calls into question whether millions of people who have bought coverage on the federal health exchanges are entitled to subsidies.

In April, the U.S. Court of Appeals for the District of Columbia Circuit, just one rung below the Supreme Court, will hear three consolidated cases challenging the Environmental Protection Agency’s right to use a provision of the Clean Air Act to regulate greenhouse-gas emissions from power plants.

“The Supreme Court’s docket in recent terms looks a lot like an outline for a stump speech for a 2016 [presidential] candidate. Immigration, check. Climate, check. Health care, check,” Doug Kendall, president of the Constitutional Accountability Center, said in an e-mail. “The court is deciding just about every major question that divides Americans along ideological lines.”

In addition to the ongoing immigration suit from the 26 states — 24 of which are led by GOP governors — House Republicans are considering filing their own suit against the administration over its immigration actions.

President Obama announced new action to delay the deportation of about 4 million undocumented immigrants living in the U.S. Here are some numbers to know about immigration. (Julie Percha/The Washington Post)

“I guess we’re getting used to getting sued,” White House senior counselor John D. Podesta quipped in an interview last week, just before he stepped down from his West Wing role.

The pending case over the Affordable Care Act — passed in 2010 — shows how in the never-ending political fight between the parties, even the passage of major legislation through Congress does not constitute a permanent victory, said Jonathan Oberlander, a professor of health policy at the University of North Carolina at Chapel Hill.

“It’s really incredible they attained the unattainable, and now the question is whether they can keep it,” Oberlander said of Democrats.

One senior Senate Democratic aide, who asked for anonymity in order to discuss party strategy, said one reason Senate leaders pushed so hard in the last Congress to seat Obama’s nominees on the D.C. Circuit was that “having judges who may be more sympathetic to the administration’s view is not an insignificant way of safeguarding against” legal reversals.

Hanen, a George W. Bush appointee, has been critical of Obama’s immigration policies in other cases.

In the last Congress, the Senate confirmed four of Obama’s nominees to the D.C. Circuit, which hears many challenges to executive actions. Active Democratic appointees now outnumber Republican ones there 7 to 4.

Jeffrey R. Holmstead, a partner at the law firm Bracewell & Giuliani who represents several electric utilities, said Democrats should not be so confident, especially since the more conservative Supreme Court will have the final say in many of these cases.

On immigration, Democrats and Republicans scrambled Tuesday to determine how Hanen’s ruling would affect a showdown over GOP demands to make funding for the Department of Homeland Security, which expires next week, contingent on halting Obama’s “deferred action” program. The White House has threatened to veto any legislation if it contains language overturning the president’s immigration programs. Such a veto could lead to a partial DHS shutdown.

RELATED: What we know and don’t know about the fight over DHS funding

Obama issued his immigration orders shortly after the midterm elections in November, saying he could no longer wait on Congress to reform border-control laws that have left more than 11 million illegal immigrants in limbo. An effort to pass a comprehensive immigration bill failed last summer.

But in his lengthy memorandum opinion, Hanen ruled that no law gave the administration the power “to give 4.3 million removable aliens what the Department of Homeland Security itself labels as ‘legal presence.’ In fact, the law mandates that these illegally-present individuals be removed.”

Hanen’s decision was a major, if temporary, defeat for the administration, which argued that the case should be thrown out because it is “based on rhetoric, not law.”

“This ruling underscores what the president has already acknowledged publicly 22 times: He doesn’t have the authority to take the kinds of actions he once referred to as ‘ignoring the law’ and ‘unwise and unfair,’ ” Senate Majority Leader Mitch McConnell (R-Ky.) said Tuesday.

The White House has said the president’s actions were based on the practice of “prosecutorial discretion,” which allows law enforcement agencies with limited resources to set priorities.

“The Supreme Court and Congress have made clear that the federal government can set priorities in enforcing our immigration laws — which is exactly what the president did,” White House press secretary Josh Earnest said.

Hanen based his temporary injunction on his belief that the administration, in making such a broad change to what current law “mandates,” at the very least did not comply with the elaborate rulemaking process of the Administrative Procedure Act, the nearly 70-year-old stature that governs how federal agencies implement regulations — including its 90-day notices and comment periods.

He said the case should go forward rather than be thrown out, as the administration has urged.

Immigration advocates charged that Hanen had narrowly “cherry-picked” his ruling and said they would urge immigrants to keep preparing their applications.

“Our message to our members and to families who are preparing for deferred action is: Don’t panic. Keep preparing,” said Debbie Smith, associate general counsel of the Service Employees International Union, which filed a legal brief in support of the administration. “We think this is a timeout, a bump in the road.”

If opponents of the president’s health-care, climate and immigration policies prevail in court, it is unclear what Republicans would propose as replacements. Three House panels have just begun working on alternatives to the Affordable Care Act, but Republicans remain opposed to mandatory limits on carbon from power plants and have yet to draft a comprehensive immigration bill of their own.

“They’re tearing stuff down without trying to offer any alternative if this thing crashes,” said Simon Rosenberg, founder of NDN, a liberal think tank. The administration, he added, is “confident the laws are behind them, but they are aware this is out of their hands. We don’t know what will happen.”

“There’s a level of chaos that could affect the health-care system and the entire functioning of DHS,” Rosenberg said. “[Republicans] are not taking responsibility for the chaos they’re creating. If they win, what are they going to do?”

Fred Barbash contributed to this report.