Progressive favorite Sen. Elizabeth Warren (D-Mass.) appeared at a campaign stop with Hillary Clinton Monday, joining the presumptive Democratic nominee to attack Donald Trump's claims of being a populist hero.

A day before Trump's planned speech on trade, Clinton argued that the Republican is not truly concerned about American jobs.

"Maybe we shouldn’t expect better from someone whose most famous words are 'you’re fired,'" she said during a speech in Cincinnati, Ohio.

"He rails against other countries, doesn't he? He says he’s for our workers," she continued. "But Trump’s own products are made in a lot of countries that aren’t named America. Trump suits were made in Mexico -- he could have had made them in Brooklyn, Ohio. Trump furniture is made in Turkey instead of Cleveland. Trump barware is made in Slovenia instead of Toledo. How does that all fit into his talk about 'America first?'"

Trump has tapped into frustration over jobs and trade, particularly concern that companies are sending jobs overseas. Clinton's Democratic opponent, Sen. Bernie Sanders (I-Vt.), played to those sentiments as well, and Bernie-or-bust voters are skeptical of whether they can trust Clinton's commitment to Sanders' economic policies.

Warren, who has gained a national profile railing against Wall Street, could boost Clinton's credibility on the topic. The potential vice presidential pick endorsed Clinton on June 9 after holding out for months, and now is out on the trail speaking on her behalf.

She introduced Clinton by invoking the #ImWithHer hashtag the campaign has promoted -- "I'm here today because I'm with her" -- and attacking Trump.

"Donald Trump says he'll make America great again. It's stamped on the front his goofy hat," she said to laughs. "But when Donald Trump says 'great,' I ask, great for who, exactly? For millions of kids struggling to pay for an education? For millions of seniors barely surviving on Social Security? For families that don't fly to Scotland to play golf? When Donald Trump says he'll make America great, he means he'll make it even greater for rich guys just like Donald Trump."

Cheered on by a raucous crowd, Warren tore into Trump for celebrating Britain's vote to leave the European Union because it "might bring more rich people to his new golf course." She also criticized the Republican for suckering students into signing up for his "fake" Trump University so he could "bleed them dry" while he turned a profit.

"What kind of a man does that?" Warren continued. "I'll tell you what kind of a man: a small, insecure, money-grubber who fights for no one but himself. What kind of a man? A nasty man who will never become president of the United States."

Clinton said she loved how Warren "gets under Donald Trump's thin skin" and "exposes him for what he is: temperamentally unfit and totally unqualified to be president of the United States."

Clinton's speech ran through a number of promises on the economy, along with attacks on Trump for his comments on Muslims, the Brexit, guns and same-sex marriage.

She vowed to block the Trans-Pacific Partnership and to take on Wall Street, along with fighting climate change, building infrastructure, raising the minimum wage and overturning Citizens United.

“We’re going to compete and win in the global economy by not letting anybody take advantage of our workers,” she said. “Not China, not Wall Street, not anyone.”