Donald Trump is no stranger to lawsuits. During his career, he's been sued nearly 1,500 times and sued others even more than that. Right now, as the presumptive Republican nominee for president, he's the subject of more than 50 civil suits.

But the lawsuits over the defunct Trump University clearly have Trump rattled. Since February, he's made the judge in the case, Gonzalo Curiel, a target of racist insults, arguing that Curiel's Latino heritage means he can't judge fairly. Given that hearings and court dates are scheduled throughout the summer before a trial begins in November, the controversy isn't going away.

Trump has good reason to fear the lawsuits over Trump University: They put lie to a central plank of his campaign. The disappointed students suing him argue that Trump is not a wildly successful entrepreneur or a canny dealmaker but rather a fraudster who made promises he couldn't keep. The legal proceedings have already revealed the details of the Trump University scam. Thanks to an order from Curiel, they could also reveal a closely guarded secret: Trump's net worth.

Even worse, the targets of Trump University look very much like Trump's voters: middle-class Americans who think he can solve their problems and provide them with a better life. Trump's campaign rests on the promise that he will turn his nastiness outward in order to help the country — that he will, in his words, be "greedy for the United States." The Trump University case suggests that even when Trump was purporting to uplift others, he was mostly enriching himself.

Trump University, later renamed the Trump Entrepreneur Initiative, folded in 2010. But it lives on in three lawsuits still making their way through the courts. The lawsuits all make essentially the same claim: that Trump University was a scam. Donald Trump didn't "handpick" the instructors, and his only goal was to persuade people to keep paying in hopes of gaining access to his real estate secrets.

Lawsuit 1: Cohen v. Trump, the case that could reveal Trump's net worth

The basic charge at the heart of two class-action lawsuits against Trump — Cohen v. Trump and Low v. Trump — is that his "university" was a fraud.

Both cases are overseen by Curiel in the Southern District of California. And while Curiel hasn't always given the plaintiffs everything they want, two of his rulings in particular have hit Trump where he's vulnerable. (Mother Jones's Kevin Drum has a good rundown of some of the key decisions in both cases.)

First, Curiel allowed one lawsuit, Cohen v. Trump, to go forward in the first place as a class-action lawsuit under RICO, the federal anti-racketeering law. The case is on behalf of anyone who purchased Trump University classes after January 1, 2007, and because of the way RICO cases work, it could end up being very expensive: Hundreds or thousands of people could get triple their money back.

Then in July 2015, Curiel ruled that Trump would have to do what many observers suspect he fears. He'll have to talk about how much he's actually worth under penalty of perjury. A magistrate judge had decided that Trump wouldn't need to reveal his net worth or respond to questions about how much money he'd put into, or made in profit, from Trump University. People could just Google how much Trump is worth, he'd said.

Curiel reversed that ruling. "It is not fair to say that Trump’s net worth is equally available … from publicly-available sources," his ruling read in part. "Publicly available figures of Trump’s wealth have been the subject of wild speculation and range anywhere from $4 to $9 billion."

Besides, Curiel continued, Cohen's lawyers wanted more specific information than just net worth, and it was fair to ask how much Trump had profited from the university that bore his name.

Then last week, Curiel granted a request from the Washington Post to unseal Trump University's "playbooks" — documents outlining how Trump University events worked that Trump argued should be kept from the public because they contain trade secrets.

Those orders allow Cohen's lawyers to gore Trump in his soft underbelly. You can call Trump a racist or a demagogue or a know-nothing, but what he's really sensitive to is the charge that he isn't as good of a businessman as he appears. That's why, many speculate, he's so reluctant to release his tax returns.

And Curiel's orders now allow a legal attack on two fronts: first, that Trump defrauds not just his opponents or the people he makes deals with but his own admirers. And second, that Trump isn't as rich as he claims to be.

The next hearing is scheduled for July 22, 2016 — the day after Trump will speak at the Republican National Convention to formally accept his party's nomination for president. Curiel will consider a motion from Trump's lawyers to make the case an individual suit rather than a class action, as well as dueling requests about what testimony will be included.

A final pretrial conference is set for August. But given the way the justice system works, it's likely to be much longer before the case actually goes to trial.

Lawsuit 2: Low v. Trump, an epic legal battle where the lead plaintiff quit

The second lawsuit in Curiel's court has a much longer history. Now called Low v. Trump, it was filed in 2010 as Makaeff v. Trump. In 2014, after years of legal wrangling, Curiel certified it as a class-action lawsuit in New York, California, and Florida but denied the plaintiffs' request to certify a class-action lawsuit in all 50 states.

The arguments about what Trump did wrong are basically the same as in Cohen v. Trump, but Low v. Trump has featured a side drama. Trump sued the initial plaintiff, Tarla Makaeff, and lost, although Curiel reduced the amount of court costs she could claim from $1.3 million to $790,000.

Then, after spending five years as the lead plaintiff and successfully defeating Trump in his countersuit, Makaeff decided she wanted out, saying she worried that the stress of the trial would damage her health.

"Trump was a celebrity when the case was filed, but no one could have anticipated that he would become a viable presidential candidate and a 24/7 media obsession as this case neared trial," her lawyers wrote in a court filing. "Subjecting herself to the intense media attention and likely barbs from Trump and his agents and followers simply would not be healthy for her."

Curiel allowed Makaeff to withdraw, which Trump's lawyers opposed, arguing they'd been preparing to attack her credibility. But he barred her from benefiting from the class-action suit should her fellow plaintiffs win.

The trial in the case has been scheduled for November — after the election.

Lawsuit 3: The state of New York's case against Donald Trump

Trump hasn't made any racist attacks on the judge in another case against him, but it's worth noting anyway.

The New York attorney general, Eric Schneiderman, is known for high-profile lawsuits that liberals love. In 2013, he was pursuing for-profit colleges — one of which was Trump University.

The lawsuit, People of the State of New York v. the Trump Entrepreneurship Initiative, accused Trump University and Trump himself of fraud, deceptive practices, false advertising, violating state rules for educational institutions, operating an unlicensed school, and disregarding buyers' rights to cancel a transaction. It sought millions of dollars of damages.

Trump's response was to sue Schneiderman, a suit that was thrown out. A trial court initially ruled that Schneiderman was filing his suit against Trump too late, throwing out most of the charges against him. But in March, a state appeals court decided the statute of limitation hadn't passed and that it could include evidence from up to six years ago about Trump University's deceptive practices.

The lawsuit is now being appealed to the state's highest court, meaning it's unlikely to be heard before November.

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