Marco Rubio is starting to go after Donald Trump

Sen. Marco Rubio (R-Florida) is starting to more aggressively attack business mogul and Republican front-runner Donald Trump on the presidential campaign trail.

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Coming off a disappointing fifth-place finish Tuesday night in the New Hampshire primary after a disastrous debate performance last weekend, Rubio told supporters "that will never happen again."

Now campaigning in South Carolina, he's going harder after Trump, who ran away with a victory in New Hampshire and is leading the polls in the Palmetto State by a wide margin.

See Rubio on the campaign trail:

"Donald Trump has zero foreign-policy experience," Rubio said during an event in Okatie, South Carolina. "Negotiating a hotel deal in another country is not foreign-policy experience."

He then criticized Trump for using profane language during a recent event in New Hampshire.

"Even in our political culture I teach my kids to be respectful. There are certain words you don't say," Rubio said, adding, "You turn on the TV and a leading presidential candidate is saying profanity from a stage."

"Profanity from a stage," he repeated.

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That was a reference to Trump's repetition of a crude statement made at a rally by someone in the crowd about Sen. Ted Cruz (R-Texas). Trump then jokingly "reprimanded" the person for saying it.

Rubio is stepping up his attacks after being widely mocked for repeating the same talking point multiple times — even as Gov. Chris Christie of New Jersey (R) ripped him for doing so. He then repeated another talking point, seeming to notice the mishap, just two days later.

During his event, an apparent supporter offered an interesting take on the accusations around Rubio.

As far as "the robot stuff," the man said, "let's keep in mind that the Terminator was elected twice in California," referring to former Gov. Arnold Schwarzenegger of California.

Rubio smiled, looked off in the distance, then glanced back toward the man.

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