South Carolina Gov. Nikki Haley described Donald Trump as someone a parent would not want to model for their children, unlike Florida Sen. Marco Rubio.

"Donald Trump is everything we hear and teach our kids not to do in kindergarten," Haley told ABC News' George Stephanopoulos on Sunday. "We have seen this behavior over and over again that's unacceptable."

This isn't the first time Haley has criticized the billionaire candidate. Delivering the Republican response to the president's State of the Union address in January, Haley took aim at Trump, urging voters to resist the temptation to "follow the siren call of the angriest voices."

Haley said Sunday that even Rubio's recent attacks on Trump, which include shots at the former reality television star's appearance, offer a kind example for America's youth.

That "is exactly what we tell our children also," Haley said. "If a bully hits you, you hit back."

Rubio "hit back and he showed that's he's willing to lead. He's willing to fight," she added. "And he's going to have the passion to do it."

She rejected the suggestion that Rubio is stooping down to Trump's level.

"I don't know if you stoop to the same level," Haley said. "When a bully comes after you, you go back. I think he punched. I think he punched hard. I think it was on policy. I think he made sure that everybody understood that there are a lot of questions that Donald Trump hasn't answered."

Haley endorsed Rubio for president on Feb. 17, before her state's Republican primary.