"I would prefer not to get into this situation where we're attacking one another," he told George Stephanopoulos on “Good Morning America,” but the perception of Trump as an "invincible force" has persuaded him to change his strategy.
"In my whole life I've had to fight and I'm going to fight now, because there is no way that the party of Reagan and the conservative movement, I'm going to allow it to be taken over by a con artist," he said.
While Rubio and Trump have not attacked each other much on the campaign trail, the Florida senator went after the business mogul Thursday night on several topics, including his tax returns and his use of foreign workers in his businesses.
Trump blasted the more combative style after the debate, telling ABC News that Rubio was a "lightweight."
And Rubio dismissed suggestions that his new strategy comes too late in the race. "We are going to win Florida," he said.