Hillary Clinton and Elizabeth Warren on the campaign trail in Ohio. AP Photo/Andrew Harnik Sen. Elizabeth Warren's attacks on presumptive Republican presidential nominee Donald Trump are hitting the campaign trail.

Appearing with Hillary Clinton in Ohio on Monday, the populist Massachusetts senator repeatedly laid into Trump, calling him a "thin-skinned bully" and "a nasty man who will never become president of the United States."

Over 15 minutes, Warren railed against the real-estate magnate's aggressive business tactics, noting a high-profile lawsuit filed against Trump University as well as Trump's claim that the UK's Thursday decision to leave the European Union would "bring more rich people to his new golf course."

"That's who Donald Trump is," Warren said. "The guy who wants it all for himself. And watch out, because he will crush you into the dirt to get whatever he wants."

Warren also alluded to Trump's rhetorical jabs at her, mocking his "Make America Great Again" trucker hats.

"You want to see goofy?" Warren said. "Look at him in that hat."

Even in her praise for Clinton, Warren still deviated to attack Trump. The senator noted Clinton's career-long battle with Republicans before quickly alluding to the real-estate mogul's inflammatory social-media presence.

"She doesn't whine — she doesn't run to Twitter to call her opponents fat pigs or dummies," Warren said.

"You know, I could do this all day," she added. "But I won't."

Standing onstage with Warren while she delivered her diatribe against Trump, Clinton seemed to relish the one-liners, telling the audience that she admired how Warren "tells it like it is."

"I do just love to see how she gets under Donald Trump's skin," Clinton said.