Mitt Romney: Family separations at border a 'dark chapter in American history'

"This was a heartbreak," Romney said at the debate, in response to a question about immigrant family separation. "This was a dark chapter in American history, to see children separated from their parents."

"This is inexcusable, and can't go on," the Senate candidate said.

Romney faces off in November against Democratic opponent Jenny Wilson, a member of the Salt Lake County Commission.

In May, the Trump administration announced a policy where authorities would criminally prosecute anyone who crossed the border illegally. This meant that undocumented immigrants who faced prosecution were held in federal prisons, where their children couldn't be with them.

Previous administrations largely opted not to pursue criminal charges against people who crossed illegally with children, and instead mostly referred them to immigration courts.

After overwhelming pushback and intense pressure from across the political spectrum, Trump reversed course and signed an executive order in June to stop the separation of families at the border.

In July, Health and Human Services Secretary Alex Azar estimated that fewer than 3,000 children who may have been separated from their parents were in government custody.

But more than 100 children who may never be reunited with their parents remain in government custody, CNN reported in September, as officials work to rectify the crisis caused by the Trump administration's initial decision.