Hillary Clinton and Elizabeth Warren join forces for the first time and unleash on Trump

Wearing matching blue outfits, Hillary Clinton and left-wing hero Elizabeth Warren campaigned together for the first time on Monday, leaning heavily on a message of economic populism and uniting against a common enemy — Donald Trump.

Warren seemed to be visibly enjoying herself as she unleashed on Trump during her speech introducing Clinton in Cincinnati, Ohio. The Massachusetts senator called him "a thin-skinned bully who is driven by greed and hate" and "a nasty man who will never become president of the United States."

She blasted Trump on everything from his response to Brexit to his failed Trump University. "You know I could do this all day," Warren said with a smile.

Clinton also painted Trump's candidacy as fundamentally dangerous for the country.

"I do just love to see how she gets under Donald Trump's thin skin," Clinton said with a laugh, adding that "she is speaking for all of us and we thank her for that."

Clinton's decision to campaign with Warren in Ohio, a crucial swing state in the general election, is a clear attempt to stop Trump early in the general election. Her campaign is anxious to attract leftover Bernie Sanders supporters, many of whom are turned off by Clinton's shifting positions on Wall Street and trade. Adding to Clinton's anxiety is the fact that Trump has been actively courting them in recent weeks with his anti-free trade and economic populist message. Warren offers a way to draw in those more liberal factions of the Democratic Party and perhaps even more importantly, has proven she is not afraid to take on Trump.

The cheering crowd was clearly energized by Warren and Clinton's message of economic progressivism. Cheers and clapping almost drowned out Clinton as she spoke about raising the minimum wage, cracking down on large corporations, and how she would "strengthen unions because they are the bedrock of a strong middle class in America."

Warren has become something of a darling in the Democratic party for her fiery critiques of Wall Street and even more scalding takedowns of Trump. In recent months, Warren has gone after on presumptive Republican nominee via his favorite communication medium, Twitter, calling him a "bully" who is "reckless" and "embarrassing." She also called Trump "a small, insecure, money grubber" at an event in May (a line she repeated during her speech Monday) and filmed an entire video for MoveOn about how horrible he was.

No, seriously -- Delete your account. — Elizabeth Warren (@elizabethforma)June 10, 2016

If — Elizabeth Warren (@elizabethforma)May 25, 2016

Warren is on the short list for Clinton's VP picks and their joint appearance on Monday added further fuel to speculation of a Clinton-Warren ticket. After refusing to endorse a candidate during the entire Democratic primary election, Warren said earlier this month on MSNBC's Rachel Maddow show that she's up for the job if Clinton asked her to serve. But her spot on the ticket poses a contradiction for Clinton, who also needs to woo the Wall Street donors and big banks that Warren has spent her life making an enemy of.

But it appeared that Clinton is more concerned with attracting liberal ex-Sanders voters rather than Wall Street mega-donors. She railed against corporate executives who "accept free handouts from the government with one hand and give out pink slips with the other." Clinton also blasted "unfair trade practices" and promised to "end the abuse of our market, our workers, our people."

Much of Clinton's speech sounded like it could have been written by Warren herself. The Massachusetts senator is a prominent expert on banking regulation and advocate for consumer financial protection. Before being elected senator in 2012, she was a professor of bankruptcy law at Harvard University and helped form the US Consumer Financial Protection Bureau (CFB), the government agency created after the 2007-2008 financial collapse intended to protect citizens in the financial sector.

Clinton thanked Warren for her role in creating the CFB, saying "that's what standing up and fighting to right economic wrongs looks like."

Few other Democrats, or people for that matter, have been as eager to take on Trump as Warren. During a speech at the American Constitution Society's convention two weeks ago, she called Trump "a loud, nasty, thin-skinned fraud who has never risked anything for anyone and who serves no one but himself."

Trump has shot back at Warren with an equal amount of vitriol, calling her "goofy" and "Pocahontas" in a nod to her Native American heritage.

Goofy Elizabeth Warren has been one of the least effective Senators in the entire U.S. Senate. She has done nothing!
— Donald J. Trump (@realDonaldTrump) May 11, 2016

Warren came prepared with a counter-attack on Monday. "You want to see goofy?" she said. "Look at him in that hat!"

Several hours after Warren and Clinton's event was over, Trump responded with a statement. Trump said Warren was a "sellout" and that "this sad attempt at pandering to the Sanders wing is another example of a typical political calculation by D.C. insiders."

Follow Olivia Becker on Twitter: @oliviaLBecker