CINCINNATI, June 27 (UPI) -- Sen. Elizabeth Warren appeared on the campaign trail with Hillary Clinton for the first time Monday, amid a report she is being formally vetted as a possible running mate.
An ABC News source familiar with the process said Warren is being considered as the presumptive Democratic nominee's vice presidential pick. They've already asked Warren to complete a questionnaire and for documents, the source said, and lawyers are involved in the process.
Clinton hasn't made her vice presidential pick a month ahead of the Democratic National Convention in Philadelphia but Warren is among a few Democrats the Clinton campaign is scrutinizing.
The Massachusetts senator could help win over supporters of Clinton's Democratic rival, Vermont Sen. Bernie Sanders.
Clinton, speaking after Warren, listed progressive priorities supported by Warren and Sanders: increased U.S. manufacturing, renewable energy, higher minimum wage, equal pay for women. And, she said, "we're going to finally make Wall Street, big corporations and the super-wealthy do more – which is not only fair, but which is right."
The two women spoke Monday in Cincinnati in front of a blue sign that read "Stronger Together."
Warren noted they both come from humble roots, in start contrast with Donald Trump and "rich guys just like him."
"I'm a daughter of a maintenance man who made it all the way to the United States Senate, and Hillary Clinton is the granddaughter of a factory worker who's going to make it all the way to the White House," Warren said.
Warren has become the top surrogate and critic of the Republican presumptive nominee. She has repeatedly attacked Trump in speeches and on Twitter, and endorsed Clinton earlier this month.
Monday's appearance at Cincinnati's Union Terminal was no different; she called Trump "a small, insecure money-grubber who fights for no one but himself."
"What kind of a man?" Warren said of Trump. "A nasty man who will never become president of the United States, because Hillary Clinton will be the next president of the United States."
She spoke before a capacity crowd of 2,600 people with about 500 still waiting outside.
Warren suggested Trump only cares about himself.
"When Donald Trump says great, I ask: great for who, exactly?" she said. "When Donald says he'll make America great, he means greater for rich guys just like Donald Trump. That's who Donald Trump is. ... And you have to watch out for him, because he'll crush you into the dirt."
Trump tweeted about the women before their appearance.
"Crooked Hillary is wheeling out one of the least productive senators in the U.S. Senate, goofy Elizabeth Warren, who lied on heritage," Trump tweeted.
A Monmouth poll released last week indicated Clinton would see a 3 percent increase in votes should she choose Warren as her vice president running mate. Clinton saw the biggest boost in votes -- 19 percent -- if shoe chose Sanders.