(AP Photo/Houston Chronicle, Gary Coronado, Pool)
Donald Trump.

Donald Trump has been training most of his fire over the past few weeks of the presidential race on his Republican rival Ted Cruz, but after Thursday night’s GOP debate he has a new target: Marco Rubio.

Trump, the Republican presidential frontrunner, went after Rubio on Twitter on Friday morning, calling the Florida senator “Mr. Meltdown.”

“Lightweight Marco Rubio was working hard last night,” Trump tweeted. “The problem is, he is a choker, and once a choker, always a chocker! Mr. Meltdown.”

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.

Responding to a Trump attack about his relationship with lobbyists, Rubio said: “Here’s a guy who inherited $200 million. If he hadn’t inherited $200 million, you know where Donald Trump would be? He would be selling watches in Manhattan.”

The repeated clashing came as both Cruz and Rubio are staring far up at Trump in the race for the Republican nomination. 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.

Until Thursday, Trump had focused on attacking mostly Cruz, the Texas senator, whom he has branded a “liar.” The attacks seem to have had an effect on Cruz’s campaign. Cruz recently fired his campaign’s communications director for spreading a video that misrepresented Rubio as dismissing the Bible, emphasizing that he was conducting his campaign “with the very highest standards of integrity.”

Cruz is the only one who has beaten Trump in a primary or caucus contest. He narrowly won the Iowa caucuses but finished third in South Carolina, where he was expected to do well.

Early Friday morning, Trump also retweeted some supporters who were critical of Rubio:

NOW WATCH: ‘You’re the basket case’ — here is the moment things spiraled out of control at the GOP debate

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