In April 2018, the Trump administration instituted the "zero-tolerance" policy where anyone caught crossing the border illegally was criminally prosecuted. It resulted in the separation of nearly 2,800 children.
Nielsen said at the hearing last December there wasn't a policy to separate families. She said the separations under zero tolerance happened because children can't be jailed with parents. Homeland Security officials said the secretary rejected the 2017 memo's suggestion and reiterated there was no policy to separate families. The FBI had no comment.
Merkley, of Oregon, is considering a presidential run.