Donald Trump just mocked Marco Rubio's supposedly big ears at a rally

After being bludgeoned by Florida Sen. Marco Rubio earlier in the day, Donald Trump hit back, mocking his rival's ears at a campaign rally.

The two Republican presidential candidates have been knocking each other all day Friday after they clashed at the CNN Republican debate on Thursday night.

Rubio had made fun of Trump at a campaign event on Friday for misspelling words in tweets Trump had posted attacking Rubio.

Rubio also mocked Trump for applying makeup backstage to get rid of a "sweat mustache."

So Trump turned the insult around on him.

"You ought to see [Rubio] backstage," Trump said at a rally in Fort Worth, Texas. "He was using a trowel to put on makeup. I will not say that he was trying to cover up his ears, I will not say that."

Trump also characterized Rubio as a "choker" and a "lightweight."

"I thought he was going to die," Trump said. "He was so scared, like a little frightened puppy."

Trump continued to rail against Rubio through his rally.

"He's a nasty guy," Trump said later. "I called him a nasty little guy, but I wouldn't say that. He's a nasty guy, and we don't need nasty. ... Honestly, there's no place for it."

For weeks, Trump has been focusing on attacking rival Sen. Ted Cruz, but he's now targeting Rubio after a contentious debate on Thursday.

Rubio and other Republican candidates went after Trump aggressively and often at the CNN debate in what turned out to be the biggest Trump pile-on yet. Rubio and Cruz each went on the attack against Trump over several issues including taxes, immigration, Trump's history as a reality-television host, and his business career.

Trump is the clear frontrunner in the primary contests, having won the New Hampshire and South Carolina primaries and Tuesday's Nevada caucuses. Rubio, along with Cruz, has been fighting to take Trump down and establish himself as the clear alternative.