(CNN) Hours after locking horns with Donald Trump at CNN's Republican presidential debate, Marco Rubio continued to batter the GOP presidential front-runner, repeatedly calling him a "con artist" and saying he is "wholly unprepared to be president of the United States."
"This is the most important government job on the planet. And we're about to turn over the conservative movement to a person that has no ideas of any substance on the important issues," Rubio said in an interview Friday on "CBS This Morning."
"The nuclear codes of the United States -- to an erratic individual -- and the conservative movement -- to someone who has spent a career sticking it to working people," he added.
Trump responded to Rubio's broadsides on Twitter Friday morning, writing, "Lightweight Marco Rubio was working hard last night. The problem is, he is a choker, and once a choker, always a chocker! Mr. Meltdown."
As the emerging smackdown between Trump and Rubio spilled over from the debate stage to the morning show circuit, Rubio conceded that the time had come to go after Trump.
"It's a narrower race, number one, and number two, I acknowledge we're an underdog," he said. "I would prefer not to get into a fight with other Republicans. But I would much more prefer not to turn over the party to a con artist like Donald Trump."
Rubio struck at the heart of Trump's populist appeal, saying in the interview, "I will acknowledge that there are some people watching this broadcast that are intrigued by him, because they think he's a straight talker and he fights for the little guy. But Donald Trump has spent forty years sticking it to the little guy or longer. And every time one of those businesses of his failed, you know how didn't get paid? The little guy that was working for him."
The Florida senator also responded to a report, first reported by CNN, that his campaign manager told supporters that the Rubio campaign was preparing for the potential of a contested convention as a means of securing the Republican nomination.
Asked if it was something he was "thinking about," Rubio said no, but he acknowledged that no one candidate may end up acquiring the 1,237 delegates required to win the nomination, and that in that event.
"If you look at the way it's going now, no one may have that number of delegates, and that in and of itself would trigger a convention in which after the first round, delegates are free to vote for whomever they want," Rubio explained.
"I would not prefer that to be the case, I would much rather have someone just win the nomination and end this process," he added. "But not a con artist like Donald Trump."