Allegations of fraud against a presumptive GOP presidential nominee Donald Trump's real estate university had been part of the political landscape for a while, but Texas became focus earlier this month.

The Houston Chronicle reported that a 2009 state attorney general's office investigation into Trump University was begun and then abruptly halted, with Trump's school agreeing to halt operations in Texas in 2010. Then-Attorney General Greg Abbott received a $35,000 campaign contribution from Trump three years later.

RELATED: Inside the probe into Trump University that Abbott's office launched and then ended

The fraud charges resurfaced when a lawsuit was filed in 2013, and in recent weeks the scandal exploded. Fellow Republicans denounced, and even un-endorsed Trump, when he alleged that the Indiana-born judge assigned to the case was unfit for impartial judgement because of his Hispanic heritage.

That judge, Gonzalo Curiel of California's Southern District, is assigned to determine whether the business practices of Trump University amounted to hard sales tactics, which are legal, or fraud, which is not.

So what's the difference? When does aggressive selling cross the line into fraud?

Ken Mingledorff, a Houston lawyer and former chief prosecutor at the Harris County District Attorney's Office, pointed to a landmark case from the Texas Supreme Court that laid out a legal definition for fraud, and has since been cited in federal cases.

"The elements of fraud are a material misrepresentation, which was false, and which was either known to be false when made or was asserted without knowledge of the truth, which was intended to be acted upon, which was relied upon, and which caused injury," wrote the judges in the 1990 case DeSantis vs. Wackenhut Corp.

Let's unpack that.

A material misrepresentation is anything untrue and relevant. Mingledorff said lawyers currently aspire to prove a higher standard: "methodical systematic misrepresentations." In other words: falsehoods that were intentionally designed and regularly repeated.

And attorneys must prove that the offender knew their misrepresentation was such.

The misrepresentation must be intended to be acted upon and relied upon. That means that the offenders—Trump University, in this case—must have meant for a falsehood to be a selling point of their product, not just a detail.

And the misrepresentation must cause damage or injury. The victim must have suffered some by the offender's fraudulent endeavor.

Only a trial will determine if Trump U. propagated fraud, and Trump's legal team is expected to mount a strong defense. But Mingledorff, drawing on his experience as a prosecutor and media reports of case details, speculated that the operations of the real estate school met the legal standards of fraud.

"It was really just a total lie," he said.

Misrepresentations in the case include describing the course instructors as executive real estate salespeople, handpicked by Trump, when in reality many of them had no real estate experience and Trump was almost entirely uninvolved, according to media reports.

The alleged fraud also seems to be methodical and systematic, Mingledorff said, since the false claims were laid out in promotional material and a sales playbook instructed faculty to make the false claims in enticing prospective students.

Media reports suggest the operation was focused entirely on recruiting students and little on teaching real estate sales.

A trial will likely show that those misrepresentations were acted upon and relied upon, because many former students have told media they enrolled in the course because of its affiliation with Trump, which they took as proof of its high-caliber instructors.

Injury also seems simple to prove; the highest level of Trump University cost $35,000 and students reportedly were encouraged to max out credit cards to pay. That cost, with no real rewards reaped from the program, probably hurt.