At rallies and debates over the last year, Donald Trump has repeatedly vowed to round up and deport the estimated 11 million people in the country illegally, sometimes saying he would eject them all in two years.
Over the last four days, however, the GOP presidential nominee and his top aides have issued contradictory signals as to whether Trump is backing off that core campaign pledge.
Aides have not said if Trump's plan is under review because it appears politically unpalatable with moderate Republicans, or because forced deportations of millions of people would be prohibitively expensive and probably logistically impossible.
For now, the campaign has yet to provide specifics on how mass removals would be carried out, who would be targeted, and how much it would cost.
Immigration and Customs Enforcement deported 235,413 people last year, down from a record high of 409,849 in 2012, according to ICE records.
The fall-off followed the Obama administration's efforts to target individuals who threaten public safety or national security and not deport those with clean records and strong family ties in the U.S.
Independent groups have expressed widespread skepticism that a Trump administration could dramatically ramp up that process without disrupting key sectors of the economy, tearing apart millions of families and violating civil liberties on a mass scale.
In May, a report by the right-leaning think tank American Action Forum estimated that finding, detaining, legally processing and deporting everyone who is in the country illegally would cost up to $300 billion.
To meet Trump's two-year goal, the report said, Congress would need to appropriate money to hire, train and field about 90,000 immigration apprehension agents — up from 5,000 Enforcement and Removal Operations officers today.
The government also would need to build about 1,250 immigration courts — there now are 57 such courts — and hire thousands more immigration judges and federal attorneys to process the caseload.
The think tank estimates that the lost labor and purchasing power of 11 million people — many of whom work, own businesses and pay taxes — could reduce the nation's gross domestic product by $1 trillion, equal to about $9,000 per household.
Moreover, finding millions of undocumented migrants almost certainly would entail immigration agents entering homes, raiding businesses and operating roadblocks to check identity papers to separate U.S. citizens and approved immigrants from those in the country illegally, a winnowing-out process that undoubtedly would be challenged in court.
"You will really have to tear up the social fabric to get this done," said Douglas Holtz-Eakin, head of the nonprofit think tank.
Farming, meatpacking, construction and hospitality industries would be hardest hit by labor shortages, the study concluded. In all, the private sector could lose 4 million to 6.8 million workers.
"That is something that is hard to wrap our heads around because that is just not who we are as a country," said Holtz-Eakin, former director of the Congressional Budget Office and former economic policy director for the 2008 GOP presidential nominee, John McCain.
The president has authority to order an increase in deportations, or to set new priorities for who is targeted. But except for people caught sneaking across the border, most removals require a court order, and deportation cases already are backed up for years in some jurisdictions.
With growing fears about border security since the 9/11 attacks, the Border Patrol has doubled in size to about 20,000 agents over the last decade, and now is the largest federal law enforcement agency.
The number of Enforcement and Removal Operations officers has stayed at about 5,000, however. Union leaders for immigration agents have long demanded that the deportation force be doubled in size as well.
"We need more interior enforcement, but Congress and politicians refuse to do it," Chris Crane, president of the National Immigration and Customs Enforcement Council, a union that represents federal deportation officers, said in a telephone interview.
According to ICE records, the leading countries of origin for removals last year were Mexico, Guatemala, Honduras, and El Salvador, and the majority were apprehended near the border.
But an estimated 40% of those in the country illegally arrived lawfully and overstayed their visas. Unless police apprehend them for violating other laws, the government has no clear way to find them.
Crane, the union official, believes that unleashing deportation officers would deter illegal border crossings and induce many in the country illegally to go home on their own.
"They will stop coming across this border and will stop dying in the desert … if we can just do our jobs," Crane said.
For now, Trump's intentions appear to be a moving target.
Over the weekend, his new campaign manager, Kellyanne Conway, said on CNN that Trump's long-promised "deportation force" was "to be determined." A close advisor, Sen. Jeff Sessions (R-Ala), said the candidate was "wrestling" with his deportation plan.
On Monday, Trump denied on Fox News that he was flip-flopping, but he also said he would not put people in detention centers, and would focus on first deporting gang leaders, murderers and other "bad people," which mirrors Obama's deportation priorities.
He even appeared to praise Obama's deportation record.
"What people don't know is that Obama got tremendous numbers of people out of the country. [President George W.] Bush, the same thing," Trump said. "Lots of people were brought out of the country with the existing laws. Well, I'm going to do the same thing."
He wouldn't say directly if he was rethinking his mass deportation strategy, saying, "I just want to follow the law."
At a campaign rally in Akron, Ohio, earlier Monday, Trump repeated his pledge to build a massive border wall and to make Mexico pay for it, but he didn't bring up mass deportations.
Then during a Fox News town hall broadcast Tuesday night, Trump said he would be open to "softening" his immigration stance to accommodate people who are law-abiding and have children who are U.S. citizens.
"There could certainly be a softening because we're not looking to hurt people. We have some great people in this country," he said, adding that he will issue his deportation plan "very soon."
"Is this a trial balloon? Are they trying to figure out how his base will react?" asked Alfonso Aguilar, who headed the office of citizenship at U.S. Citizenship and Immigration Services in the Bush administration and now heads the Latino Partnership for Conservative Principles.
Trump could be more competitive with Latino voters if he softened his tone and clarified his immigration position, Aguilar said in a telephone interview from San Juan, Puerto Rico.
One option would be to require undocumented immigrants without a criminal record to "touch back" with their country's embassy or consulate in the United States rather than demanding they leave and apply to come back in, he said.
"Logistically it would be more practical and also it is humane," Aguilar said.
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7:55 p.m.: The story was updated with remarks Trump made on his deportation plan during a Fox News town hall gathering.