The Democrats have released their attack dog on Donald Trump.

On Thursday evening, Massachusetts Senator Elizabeth Warren dug into the presumptive Republican nominee. She slammed Trump for his "racist" comments about a federal judge, and for the legally questionable business practices that have landed him in court, CNN reports.

"Donald Trump is a loud, nasty, thin-skinned fraud who has never risked anything for anyone and serves nobody but himself," she said in front of a crowd at the American Constitution Society, a lawyers' group that advocates for progressive policy.

Warren called out Trump for distasteful remarks in his ongoing spat with a federal judge, Gonzalo Curiel, who is presiding over a case involving Trump University. The business mogul alleged that Judge Curiel — who was born in Indiana — was biased against him because of his Mexican heritage.

The back-and-forth has been one-sided, since Judge Curiel is bound by a federal code of ethics, a dynamic that Warren noted in her speech.

"Trump is picking on someone who is ethically bound not to defend himself — exactly what you would expect from a thin-skinned racist bully," Warren said.

AP/John Minchillo - apimages.com

The Massachusetts senator isn't the only prominent politician to call Trump's comments racist. This week, the country's top Republican, Speaker Paul Ryan, said the remarks were the "textbook definition of a racist comment." Ryan said he would still support Trump, though.

Judge Curiel is hearing two class-action lawsuits from former Trump University students, who say they were defrauded. Trump is named as a defendant in both cases, the Washington Post reports.