Newly released documents about a now-defunct business owned by Donald Trump reveal strategies for enticing people to enrol in real estate seminars even if they couldn't afford it.
The revelation provides fresh fodder for Hillary Clinton's claim the presumptive Republican nominee took advantage of vulnerable Americans.
"Trump University was a fraudulent scheme used to prey upon those who could least afford it," Clinton's campaign wrote on Twitter on Wednesday morning.
Clinton has previously hammered Trump for cheering on the collapse of the US housing market and for failing to make good on pledges to donate to veterans until pressure from the media.
Trump University is the target of three lawsuits that accuse the business of fleecing students promising to teach secrets of success in real estate.
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Plaintiffs contend that Trump University gave classes that were like infomercials, constantly pressuring customers to buy more and, in the end, failing to deliver.
As Trump steamrolled through the GOP primary, some of his rivals raised Trump University as a liability for the businessman.
While details about the business did little to stop Trump in the primary, Clinton allies say GOP candidates were too slow in raising concerns and inconsistent in their attacks.
The documents released on Tuesday include the "playbooks" for Trump University, which outline how employees should guide customers through "the roller coaster of emotions" once they have expressed interest in the courses.
Trump University offered a three-day seminar for $US1,495 ($A2,068), using it as a springboard to sell more expensive "Trump Elite" packages for up to $US34,995 a year.
Trump University's core customers are identified in the documents as male heads of households between 40 and 54 years old with annual household incomes of at least $US90,000, a college education and a net worth of more than $US200,000.
During one-on-one conversations, "you may begin with some small-talk to establish rapport but do not let them take control of the conversation", a playbook reads.
For those who have hit credit limits, employees should suggest students dip into savings or identify other "seed capital" and "if they really believe in you and your product, they will find the money".
The documents were unsealed on Tuesday and do include testimony from several satisfied customers.
Trump has railed against US District Judge Gonzalo Curiel, who ordered on Friday the documents unsealed.
At a rally in San Diego on Friday, he accused the judge of being "hostile" and a "hater of Donald Trump", and raised questions about his ethnicity.
"The judge, who happens to be, we believe, Mexican, which is great, I think that's fine," Trump said of Curiel, who was born in the US.
The six-year-old case in San Diego is scheduled to go to trial shortly after the November presidential election.
