Rubio bashed the real estate mogul for hiring illegal workers on his building projects and for criticizing Mitt Romney's call for self-deportation as the party's nominee during the 2012 election.
"The truth is a lot of these positions he is taking are new to him," Rubio said. "In 2011, he talked about a need for a pathway to citizenship. In 2012 Donald criticized Mitt Romney, saying that Mitt lost his election because of self-deportation." 

"Even today, we saw a report in one of the newspapers that Donald hired a significant number of people from other countries to take jobs that Americans could have filled. My mom was a maid at a hotel, instead of firing an American like her, you would have brought in people from all over the world to fill those jobs."

The tack is the Florida senator's most aggressive against Trump to date, just days before the pivotal Super Tuesday's primaries, and he wasted no time in going on offense.

He took a swipe at the party front-runner during his opening remarks, asking whether the GOP will remain the party of "hopes and dreams" or "a party that simply preys on people's angers and fears."

Trump argued that he only criticized Romney because he ran a "terrible campaign ... that should have been won." And he defended the findings that he hired foreign workers for his development in Florida because it was his only option. 

"Everybody agrees with me on that," he said. 

"They were part-time jobs, we needed that or we might as well close the doors because you couldn’t get help in those hot, hot sections of Florida.”

But Rubio shot back. 

“I think it’s important that if you are going to claim that you are the only one that lifted this into the campaign, that you acknowledge for example, you were the only person on this stage who has ever been fined for hiring people to work on your projects illegally," Rubio said. 

The barbs continued to devolve; Rubio argued that Trump's fortune only came to be because of his inheritance, while Trump bashed Rubio for his own financial woes.