Amid growing outrage over the "zero tolerance" immigration policy implemented by President Donald Trump's administration in April, the president and his allies have sought to downplay the practice of separating families who cross the border illegally as nothing new.

"This has been going on for 50 years — longer," Trump said on Wednesday, hours before signing an executive order to halt the policy he put in place. "This has been going on under President Obama, under President Bush, this has been going on for many many years. We are gonna see if we can solve it. This is not something that happened just now."

This is inaccurate — there was no widespread Obama-era policy of separating parents and children — but it's a common talking point for Republican commentators and members of the president's administration. Trump's policy, now temporarily halted, aimed to prosecute every single illegal border crossing, including asylum-seekers. The government separated children from their parents or legal guardians because the adults had been referred for prosecution for illegal entry into the United States.

"The Obama administration, the Bush administration all separated families," Department of Homeland Security Secretary Kirstjen Nielsen told reporters at the White House on Monday. "They absolutely did. They did — their rate was less than ours, but they absolutely did do this. This is not new."

"This is a policy that is implemented under the Obama Administration," former Trump campaign manager Corey Lewandowski said on Fox News.

Matt Schlapp, chairman of the American Conservative Union, made a similar point on Fox News on Friday.

"You know what's ironic?" he said. "It's the same way Barack Obama did it."

Immigration advocates and former Obama administration officials say that's just not true.

The idea that this is simply a continuation of an Obama-era practice is "preposterous," said Denise Gilman, director of the Immigration Clinic at the University of Texas Law School. "There were occasionally instances where you would find a separated family — maybe like one every six months to a year — and that was usually because there had been some actual individualized concern that there was a trafficking situation or that the parent wasn’t actually the parent."

Once custody concerns were resolved, "there was pretty immediately reunification," Gilman told NBC News. "There were not 2,000 kids in two months — it’s not the same universe," she added.

The Trump administration separated 1,995 children from 1,940 adults from April 19 to May 31, a spokesman for the Department of Homeland Security said Friday, a period in which the "zero tolerance" policy was in effect.

Jeh Johnson, who served as homeland security secretary under Obama, said he did not separate children and parents despite the enormous surges of unaccompanied minors and families that came across the border in 2014 fleeing Central American violence.

"In three years on my watch, we probably deported or returned or repatriated about a million people to enforce border security. One of the things I could not do is separate a child from his or her mother, or literally pull a mother from his or her arms," Johnson said on MSNBC last week. “I just couldn’t do it.”

Obama’s top domestic policy adviser, Cecilia Muñoz, said the Obama administration did consider a similar policy, but determined it heartless.

"The agencies were surfacing every possible idea,” Muñoz told The New York Times in an interview recently. "I do remember looking at each other like, ‘We’re not going to do this, are we?’ We spent five minutes thinking it through and concluded that it was a bad idea. The morality of it was clear — that’s not who we are."

The Obama administration did detain families together — some indefinitely — in hopes of deterring future migrants back in 2014, earning protests and public outrage at the time.

"Family separation just adds injury to the insult of detention," said Bradley Jenkins, manager of the Board of Immigration Appeals Pro Bono Project at CLINIC, the Catholic Legal Immigration Network Inc. He argued the detention of asylum-seekers is "unnecessary," and that Obama-era detention centers were concerning, too.

During the Obama administration, courts intervened in several cases in which families were detained together. The detention of migrants could not be used as an effort to deter asylum-seekers, according to one ruling. According to another, the detention of minors with their parents ran afoul of the 1997 Flores settlement, a ruling that set standards for the detention of minors by prioritizing them for release to the custody of their families and requiring those in federal custody to be placed in the least restrictive environment possible.

On Tuesday, the Trump administration said they are looking for a legislative change to that legal precedent on how the government treats children in immigration custody; on Wednesday, the president announced an executive order to end the policy of child separation that he'd implemented in the Spring.

"In each and every one of our negotiations in the last 18 months, all the immigration bills, we asked for resolution on the Flores settlement that is what we view requires 20 days before you have to release children and basically parents been released with children into society," White House Legislative Affairs Director Marc Short told reporters.

The executive order Trump signed on Wednesday directs the Department of Defense to help in the housing of families, signaling that Trump now intends to detain families together much like the Obama administration did.

Just hours before signing that order, however, Trump said his family separation policy paled in comparison to his impression of the images he saw of the Obama-era family detention centers.

"You look at the images from 2014, I was watching this morning and they were showing images from 2014 and they blow away what we’re doing today," Trump said. "I saw images that were horrible."