Republican presidential candidate Donald Trump walks out to speak during a rally Monday night in Valdosta, Ga. (Jabin Botsford/The Washington Post)

A well-funded super PAC is escalating its assault on Donald Trump with a devastating new television advertisement that portrays the Republican presidential front-runner as a predatory huckster who scammed working- and middle-class Americans.

A 60-second ad, which will begin airing Wednesday on stations across the country at the cost of more than $1 million, centers on Trump University, the billionaire mogul's for-profit enterprise that promised to teach students the tricks of the real estate trade and is now defunct and the subject of a fraud suit.

The ad, titled "Scam," is the latest component of the stop-Trump campaign of Our Principles PAC, a conservative group funded in part by Marlene Ricketts, a major Republican donor and the wife of TD Ameritrade founder Joe Ricketts.

It comes amid a heightened focus on Trump's business career, including the scandal-ridden Trump University, as rival candidates and Republican groups move urgently to halt his momentum by discrediting him as a businessman and sowing doubts about his character.

“The main premises of Donald Trump's candidacy are one, that he’s this brilliant businessman, and two, that he says it like it is," said Katie Packer, a GOP strategist who runs Our Principles PAC. "If you follow this guy very closely, you find out very quickly that both are categorically false."

The group's ad opens with footage of Trump speaking in an informercial: "At Trump University, we teach success. That’s what it’s all about: success. It’s going to happen to you."

Then, the ad cuts to press clippings showing students alleging they were duped and defrauded. A male narrator says: "The truth about Trump University: Donald Trump made millions while hard-working Americans got scammed. Donald Trump belongs in 3 a.m. informercials — not here," as a picture of the White House is shown. The ad directs viewers to the super PAC's website, TrumpQuestions.com.

The ad was created by Larry McCarthy, one of the Republican Party's top media strategists who is known for his scorching attack ads, according to a source familiar with the super PAC's activities.

It will air nationally on the CNN and Fox News Channel cable channels and at a higher volume in states holding primaries in March 15, including Florida, where home-state Sen. Marco Rubio is trying to cut into Trump's polling lead.

A barrage of ads about Trump University are on the air from multiple super PACs, while on the campaign trail, Rubio as relentlessly attacked Trump over the controversy.

The American Future Fund is running a series of ads featuring testimonials from victims of Trump University who say they were hoodwinked by the allure of riches Trump promised in its marketing. Images of the three individuals delivering the testimonials appear briefly in Our Principles PAC's ad.

Trump issued a statement on Monday demanding that the American Future Fund ads be retracted.

New York Attorney General Eric Schneiderman is seeking restitution for former students who allege that Trump University bilked them out of their money with false promises. In speeches and interviews over the past week, Trump has forcefully defended himself and the company.

Packer, who served as deputy campaign manager to 2012 nominee Mitt Romney, noted that Trump could be on trial this summer for the Trump University case. She argued that Democrats would use the issue and others in Trump's business career to savage him just as they did four years ago to Romney over the private equity firm he had founded.

“Once the Democrats go all Bain Capital on this guy and trot out example after example of hard-working, innocent people whose lives were ruined by Trump’s greed, you don’t think this is going to have an impact in the general election?” Packer said. "This is a person that’s disqualified from being our party standard bearer."