Immigrants and their supporters with the group “We Are CASA” protest planned raids to deport illegal immigrants during a rally in Lafayette Park next to the White House in December. (Saul Loeb/AFP/Getty Images)

The Supreme Court announced Tuesday that it will consider whether President Obama exceeded his powers in trying to shield millions of illegal immigrants from deportation, stepping into one of the most contentious topics in the nation’s political debate.

A positive ruling from the justices would provide Obama his last chance before leaving office to protect more than 4 million people who are parents of citizens or of lawful permanent residents and allow them to “come out from the shadows” to work legally, as he put it when announcing the program in November 2014. The initiative was challenged by 26 states and has been blocked by lower courts.

The Supreme Court will find itself once again reviewing a top priority of the Obama administration; in dramatic, high-profile cases, the court twice has saved the president’s Affordable Care Act from conservative legal challenges.

This time, the justices will confront the fundamental tension of the Obama years: whether the president is using the substantial powers of his office to propel the nation past political gridlock or whether he has ignored constitutional boundaries to unilaterally impose prescriptions that require congressional approval.

The court amped up the legal importance of the case by adding a constitutional question: whether Obama’s actions violated the “take care” clause, which commands the president to “take care that the laws be faithfully executed.”

In vowing to aggressively use executive action to counter congressional inaction on his priorities, Obama has caused his greatest confrontations with Republicans and led them to claim that he disregards the Constitution.

The new case adds yet another controversy to a Supreme Court docket this term that already includes abortion rights, affirmative action and the rights of religious objectors to not provide employees with contraceptive coverage. Most or all of those decisions will land in June, just before Republicans and Democrats officially choose their nominees to succeed Obama.

The president’s immigration program, Deferred Action for Parents of Americans and Lawful Permanent Residents (DAPA), has split the presidential candidates. Republicans have said they would reverse it immediately if it ever took effect. Democratic hopefuls have said they would expand upon it.

It would allow illegal immigrants in the affected categories to remain in the country and apply for work permits if they have been here at least five years and have not committed felonies or repeated misdemeanors.

The administration says the program is a way for a government with limited resources to prioritize which illegal immigrants it will move first to deport. As a practical matter, the government has never deported more than 500,000 undocumented immigrants per year and often sends home far fewer than that.

But Texas and 25 other Republican-led states sued to stop the initiative, and a federal district judge in Texas and then a panel of the U.S. Court of Appeals for the 5th Circuit said the program could not be implemented.

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

The states said that the program “would be one of the largest changes in immigration policy in our nation’s history” and that it raised major issues involving the separation of powers and federalism.

“DAPA is a crucial change in the Nation’s immigration law and policy — and that is precisely why it could be created only by Congress, rather than unilaterally imposed by the Executive,” Texas Attorney General Ken Paxton (R) said in a filing to the court.

The Obama administration had urged the court to accept the case in time to hear it during the current term, and White House officials said they were confident their side would prevail.

Speaking to reporters Tuesday, White House press secretary Josh Earnest said Obama’s actions were “clearly within the confines of his authority as president of the United States.”

“We’ve got a lot of confidence in the legal arguments that we’ll be making before the court,” Earnest said, adding that the administration has not only a legal case to make but also a policy argument about “the practical impact, the positive impact” of the executive actions “on the security of communities across the country.”

The administration contends that the states have no legal standing to sue because it is up to the federal government to set immigration policy and that the Department of Homeland Security did not violate federal statutes in devising the program.

The government’s decision to set priorities about whom to deport was a practical response to financial constraints, the administration says. Congress has given it enough money to deport no more than about 400,000 of the nation’s estimated 11 million illegal immigrants, according to the government.

In the administration’s petition to the court, Solicitor General Donald B. Verrilli Jr. said that the lower courts had ignored “established limits on the judicial power. If left undisturbed, [the rulings] will allow States to frustrate the federal government’s enforcement of the Nation’s immigration laws.”

Verrilli said that if not reversed, the rulings “will force millions of people — who are not removal priorities under criteria the court conceded are valid, and who are parents of U.S. citizens and permanent residents — to continue to work off the books, without the option of lawful employment to provide for their families.”

The administration has challenged Texas’s legal standing to sue. District Judge Andrew S. Hanen agreed with the state that, because it would face a financial cost in providing driver’s licenses to those covered by the new program, it had standing to challenge the initiative. The administration countered that Texas was not required to issue the licenses. It should not be able to injure itself, Verrilli argued, to achieve standing to sue.

In the appeals court decision, U.S. Circuit Judge Jerry Smith rejected the administration’s argument that DAPA was a form of “prosecutorial discretion” in which a government with limited resources sets priorities for enforcement.

The program, Smith wrote, “is much more than nonenforcement: It would affirmatively confer ‘lawful presence’ and associated benefits on a class of unlawfully present aliens. Though revocable, that change in designation would trigger” eligibility for federal and state benefits “that would not otherwise be available to illegal aliens.”

The administration has made clear that it will rely heavily on a 2012 Supreme Court decision that struck down parts of an Arizona law restricting immigration and that said “the removal process is entrusted to the discretion of the federal government.”

Verrilli, in his petition to the Supreme Court, also disputed the lower court’s ruling that the DHS secretary had exceeded his authority in issuing “guidance” about how to treat the illegal immigrants.

Under the appeals court’s reasoning, Verrilli said, immigration laws allow the secretary to decide that individuals may remain in the country for a period of time but bar him “from enabling them to work lawfully to support themselves and their families while they are here. Congress did not constrain the secretary’s broad discretion to such half-measures.”

Even as Earnest, the White House press secretary, highlighted support for the administration’s position — noting that “there are other states and the District of Columbia that have filed paperwork indicating they strongly support implementation of these executive actions” — he acknowledged that it is unclear how much of the program could be implemented before Obama leaves office.

Since every Republican vying for the party’s presidential nomination has voiced opposition to Obama’s plan, Earnest observed that only Congress could deliver a lasting solution to the question of illegal immigration in the United States, since “executive actions can be reversed by subsequent presidents.”

The case is United States v. Texas.

David Nakamura contributed to this report.