The crisis on the border with Mexico is rapidly overtaking President Obama's plans to use executive action to reshape the nation's immigration system, forcing him to confront a new set of legal, administrative and political complications.
The influx of 57,000 migrant children from Central America is leading Mr. Obama to crack down on deportations at the moment he was preparing to allow more people who are in the country illegally to stay. Although White House officials insist that Mr. Obama has no intention of backing down on his public pledge to use executive orders to "fix as much of our immigration system as I can," they acknowledge that the crisis has made it much harder.
In a sign of the pressure on the president from all sides, Mr. Obama's Democratic allies in Congress, including Representative Nancy Pelosi of California and the members of the Hispanic Caucus, vowed on Wednesday to oppose his plans to make the deportation of the children easier.
"Is the only immigration bill we're going to have one that hurts children?" Ms. Pelosi said in an interview.
On Wednesday evening, senior administration officials held a briefing on the border surge for all 100 senators as new polls showed large majorities of Americans disapprove of the way Mr. Obama is handling the border crisis, even as support grows for a broader immigration overhaul. Inside the West Wing and at the Justice and Homeland Security Departments, administration lawyers have been working to find consistent legal justifications for speeding up the deportations of Central American children at the border while preparing to ease up on deportations of long-settled immigrants in the country's interior.
The challenge, according to lawyers inside and outside the government, is to avoid being arbitrary in deciding who must go and who can stay.
"It's legally complicated," said Cecilia Muñoz, the director of the Domestic Policy Council at the White House and Mr. Obama's top immigration adviser. "That was always going to be true. It's just in higher relief now."
At the same time, the members of Mr. Obama's team who would play the most influential roles in crafting unilateral policy changes are instead immersed in the urgent debate over what powers the administration has to expedite the removal of unaccompanied children crossing illegally into the United States. The Homeland Security secretary, Jeh Johnson, has traveled to the border five times since May. In Washington, he has been making daily trips to Capitol Hill to brief lawmakers on the crisis and generate support for the president's $3.7 billion emergency funding request to address the surge of Central Americans.
"Operationally, they have a huge workload at this point for the very same people and agencies that would be involved in any kind of new program" created by executive order, said Doris Meissner, who served as commissioner of the Immigration and Naturalization Service in the Clinton administration.
Politically, the surge in crossings has allowed conservatives to seize on the crisis as new evidence that Mr. Obama's policies are inviting illegal immigration across a still-porous border — and has once again set the president at odds with many Democrats and immigration activists.
In a meeting on Wednesday with Hispanic lawmakers, Mr. Obama was said to have told the group that the border crisis and his plans to ease up on some deportations had become entangled in the public's mind. Senator Robert Menendez, Democrat of New Jersey, said after the meeting that Mr. Obama conceded the border crisis "affects the sentiment of the general public about, you know, how far one can go on these issues."
But Representative Luis V. Gutiérrez, Democrat of Illinois, said the meeting made him hopeful about how far the president would go this summer in sparing some immigrants from deportation.
"What we asked the president was this: to be as broad and generous as Republicans have been small and meanspirited," Mr. Gutierrez said. "He agreed that he will be as broad as possible."
But the current border crisis, Mr. Gutiérrez said, "has complicated the issue for all of us."
White House officials said the president was well aware of the potentially explosive politics of the border crisis when he promised in the Rose Garden on June 30 that he was ready to announce executive actions later this summer.
At the time, Mr. Obama called the surge in children from Central America an "actual humanitarian crisis on the border," and said it "only underscores the need to drop the politics and fix our immigration system once and for all."
In the days leading up to the Rose Garden speech, there were discussions in the West Wing about the impact that the border crisis might have on the president's promise to use his executive authority. White House officials said they decided that while the border emergency presented a considerable public relations problem, it should not get in the way of action later this summer. In the weeks since those meetings, the crisis in the Rio Grande Valley along the border has ballooned into round-the-clock cable television fare and constant fodder for Mr. Obama's opponents in Congress.
"Republicans have decided to use the Rio Grande as a reason not to do immigration reform; we won't," said Jennifer Palmieri, the White House communications director. "The American people see immigration as an urgent issue and want the administration to act to address the problem of a broken system."
But while the public's appetite for a broad immigration overhaul may be intensifying, there is also evidence that the border crisis is tarnishing Mr. Obama's standing. A poll conducted July 8 to 14 by the Pew Research Center for the People and the Press found that the proportion of people saying it was important to pass "significant" immigration legislation had risen to 61 percent, from 49 percent in February. At the same time, the public by a nearly two-to-one margin disapproves of the president's handling of the Central American surge, with 56 percent giving him negative marks and 28 percent positive.
White House officials, without providing specifics, said the most likely executive actions that Mr. Obama would announce at the end of the summer were consistent with the administration's efforts to move away from deporting unauthorized immigrants who have been in the country for years and have not otherwise broken the law.
By shifting resources away from long-established families, they said, law enforcement can better focus on processing the asylum claims of recent immigrants and deporting those who do not qualify to stay in the United States — a rationale that Peter J. Spiro, an immigration specialist at Temple University Law School, said had long been the basis of the nation's current immigration system.
"There's this longstanding distinction between undocumented immigrants who are inside the United States versus those who are outside trying to get in," he said.
Immigration advocates continue to argue that the renewed emphasis on the border only sharpens the incentive for the president to take expansive executive action to protect more unauthorized immigrants.
"Obama's legacy's on the line," said Frank Sharry, the executive director of America's Voice, an immigration overhaul lobbying group. "Does he really want to go down as the 'deporter in chief,' and the only thing that happened during his second term was beefed-up enforcement and deportations? He's the president. He's got to take action."
— By Julie Hirschfeld Davis and Michael D. Shear, The New York Times. Ashley Parker and Jonathan Weisman contributed reporting.