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"Chris is a dear friend, but none of us understand why he did this," Haley said Sunday in an exclusive interview on ABC's "This Week." "What I will tell you is Donald Trump can't beat Hillary Clinton."
Haley, who endorsed Florida Sen. Marco Rubio before Trump won her state's Republican primary last weekend, said it would be impossible for Trump to win a general election because he is capped at 35 percent support.
"Marco Rubio is the only one that can defeat Donald Trump and Marco Rubio can beat Hillary Clinton and will win in November," she said.
Haley said Trump is everything "we teach our kids not to do in kindergarten." She added Rubio's recent jabs at Trump show he was willing to lead and fight with passion and is "exactly what we tell our children also -- if a bully hits you, you hit back."
In a separate interview on "This Week," Christie admitted he still disagrees with Trump on some of his policy proposals despite endorsing him.
"This is now a choice, and of the candidates remaining on that stage, he is the best person to beat Hillary Clinton, which is job one for Republicans," Christie said. "He is the best person to beat her and he is the best person to help keep America safe."