Hillary Clinton has called Donald Trump a fraud for ripping off students at his Trump University.
Her claim comes as the two likely presidential candidates are almost neck-and-neck in a national poll.
Newly released federal court documents gave Ms Clinton all the ammunition she needed.
"This is just more evidence that Donald Trump himself is a fraud," she says. "You can't make this up."
She quoted managers at the now-defunct Trump University, who said that the real estate school's business model was "a total lie" that "preyed upon the elderly and uneducated".
"Trump and his employees took advantage of vulnerable Americans, encouraging them to max out their credit cards, empty their retirement savings, destroy their financial futures, all while making promises they knew were false from the beginning," Ms Clinton says.
Taking a page from Mr Trump, Ms Clinton kept up the assault online, with a barrage of tweets calling Trump University a "con" that "intentionally put people at risk".
But Mr Trump isn't the candidate being scrutinised by federal authorities.
Ms Clinton's email server is the focus of a long-running FBI investigation.
In a new national Quinnipiac poll, both candidates get low marks for honesty, though Mr Trump does slightly better.
Speaking in Elkhart, Indiana, today, US President Barack Obama went after Mr Trump's plans to lower taxes for the wealthy.
"That will not bring jobs back, that is not fighting for the American middle class, that will not help us win," Mr Obama says.
"That is not going to make your lives better, that will help people like him."