Five former Trump officials and conservative allies told Reuters that even as Trump weighs harsher anti-migrant measures, they are concerned about implementing a new version of the 2018 "zero tolerance" policy that separated thousands of children from their parents at the southwest border.

They said they worry about a repeat of the widespread public backlash provoked by the original policy.

"The family separation that resulted from the zero tolerance caused an uproar in the country," said Tom Homan, a former Trump immigration official who could join a second administration. "The best way to do it, rather than deal with all that chaos that comes with it, is to keep them in a residential center together and have their hearings together."

Trump is the leading candidate for the Republican Party's 2024 presidential nomination and has made border security a major theme of his campaign. He is vowing to restore the hardline policies from his 2017-2021 presidency, and implement new ones that clamp down further on both legal and illegal immigration.

Trump touted the efficacy of family separations during a CNN town hall in May, and declined to rule out reinstating them. He defended them again in an interview with Spanish-language television channel Univision that aired on Nov. 9.

"It stopped people from coming by the hundreds of thousands because when they hear 'family separation,' they say, 'Well, we better not go.' And they didn't go," he said.

Trump's hardline position has been seized upon by Democratic President Joe Biden's re-election campaign, which says it is an example of the "extreme" policies the Republican would pursue if he returned to the White House.

Civil rights activists are alarmed by Trump's comments and are ready to return to court to fight any new version of the policy, they told Reuters.

The Trump campaign did not respond to requests for comment.

'LOT OF WAYS TO DO THIS'

How to handle the thousands of families crossing the southwest border illegally has bedeviled successive Republican and Democratic administrations. Biden has struggled with record numbers of migrants crossing the border illegally since he took office, including a recent rise in families.

The Trump administration launched its "zero tolerance" policy in April 2018 as a way to discourage illegal border crossings, including by families. Under the policy, parents were charged with immigration crimes and sent to jails while children were placed in shelters.

Trump ended it in June 2018 amid the backlash and instead said he would seek to detain families together. But family detention remains limited to 20 days under a 2015 court order, typically not enough time to process family asylum claims and potentially deport them.

With some opinion polling showing battleground state voters favoring Trump over Biden on immigration issues, Biden's campaign is reminding them about Trump's separation policy, which was unpopular among most Americans, including some Republicans.

"Trump has been unapologetically open about the extreme, inhumane, and fundamentally un-American policies that he would enact," Biden campaign manager Julie Rodriguez said on a Nov. 18 press call before a Trump border visit.

Among the Trump actions that Rodriguez highlighted was family separation, calling it a "cruel policy of ripping babies from their mothers' and fathers' arms."

Homan said he was not sure what he would do if Trump asked him to revive family separation.

"I would suggest there are a lot of ways to do this," he said. "I'd have to cross that bridge when we get to it."

Homan added that it would need "more safeguards in place to make sure these families get reunited quickly."

Chad Wolf, Trump's former acting homeland chief and current executive director of the America First Policy Institute, a Trump-aligned think tank, said "all options need to be on the table" when asked about revisiting family separations.

But Wolf said the U.S. public clearly did not support it and that other actions could achieve the same goal.

ACTIVISTS READY LEGAL FIGHT

If Trump did implement a family separation policy, he would likely face legal challenges. Days after he ended "zero tolerance" in 2018, a federal judge ordered the administration to reunite the families in response to a lawsuit brought by the American Civil Liberties Union (ACLU). The effort is still ongoing due to lack of record-keeping.

Another hurdle for Trump could be a settlement agreement signed by the Biden administration that would bar similar separations for eight years.

ACLU attorney Lee Gelernt said the group would go to court to enforce the prohibition if separations resumed.

"We take very seriously the recent talk about it still being on the table and will be prepared if it happens again," he said.

Mark Morgan, a top border official under Trump, said he does not believe a new Trump administration would implement a family separation policy in the way it did the first time.

Morgan - like Homan, Wolf and others - cited Trump's 2019 "remain in Mexico" policy as a better option. That program forced certain non-Mexican migrants to wait in Mexico for the resolution of their U.S. cases and coincided with a drop in border apprehensions, including of families.

Biden moved to end "remain in Mexico" but Trump has pledged to bring it back if reelected.