Republican candidate Mitt Romney called family separations at the border a "dark chapter in American history" during a Utah Senate debate Tuesday night.

When asked about the policy, Romney, a former GOP presidential nominee, described the separations as cruel.

"This was a heartbreak," he said.

"This was a dark chapter in American history to see children separated from their parents and to see, as you've described, a young child that hasn't seen their parents in a long time. This is inexcusable and can't go on."

The Trump administration announced a "zero-tolerance" policy at the southwest border earlier this year, meaning that anyone crossing over would be criminally prosecuted. As a result, adults caught crossing illegally were held at federal prisons, and separated from their children.

After intense pressure, this separations were halted by an executive order signed in June.

Romney's run to replace outgoing Sen. Orrin Hatch (R) is first foray into politics since his failed 2012 presidential bid.

Romney's challenger is Salt Lake County Councilwoman Jenny Wilson (D).

The Cook Political Report, a nonpartisan forecaster, rates the race as "Solid Republican."