Marco Rubio vows to unmask Donald Trump "for the con man that he is" before he destroys the Republican Party.
Rubio also insisted that he will win his home state of Florida despite polls showing Trump leading.
It was part of a day full of personal insults hurled between Rubio and Trump that started on the debate stage Thursday night.
While Rubio acknowledged that Trump is the GOP frontrunner, he indicated he would not support the Republican presidential ticket if Trump is on it.
"The Republican Party would be split apart if he's the nominee," Rubio told reporters in Oklahoma City Friday.
"We will lose this election of Trump is the nominee," he said later at a rally.
Trump has done "the ultimate con job on the American public," Rubio said. "We're going to unmask him for the con man that he is."
Trump is not the business genius he purports to be and has suffered "colossal business failures," Rubio said. If not for a $200 million inheritance from his father "he'd be selling watches in Time Square."
Donald Trump has spent a career sticking it to working Americans. https://t.co/tusArgR8yb-- Marco Rubio (@marcorubio) February 26, 2016
Trump's response was to make fun of Rubio for his intense sweating during the debate, suggesting the younger candidate was a lightweight who folded under pressure.
Never let them see you sweat! pic.twitter.com/qygVFf6JFF— Donald J. Trump (@realDonaldTrump) February 26, 2016