CINCINNATI — It was a photo-ready moment designed to produce images of the Democratic party uniting to take on presumptive Republican nominee Donald Trump.

Hillary Clinton gushed over Elizabeth Warren, calling her “my friend’’ and “a great leader.’’ Warren praised Clinton as a “fighter’’ who “tells it like it is.’’

The two women raised their clasped hands in the air.

Not only did their first joint appearance of the 2016 presidential campaign feature a symbolic joining of the liberal and centrist wings of the party, but it was another phase of Warren’s audition for vice president. The Massachusetts senator is among a handful of candidates being vetted by Clinton’s team to be her running mate.

“I’m here today because I’m with her,’’ Warren said, echoing Clinton’s campaign slogan, pointing to Clinton, and whipping up the ecstatic crowd at a historic train station.

Warren hasn’t always been with her — in December when 13 members of the 14 female Democratic senators endorsed Clinton, Warren was missing.

She sat on the sidelines before Iowa, when polls showed that Clinton needed a liberal boost. She sat out New Hampshire, when Clinton was clobbered with a 22-point loss. She stayed silent before the Massachusetts primary, which Clinton won by only 17,000 votes.

But now with the Democratic party facing Trump in November, Warren is signaling to her legions of liberal supporters that the time has come to put party differences aside and enthusiastically back the standard-bearer.

“When Donald Trump says he’ll make America great, he means he’ll make it greater for rich guys like Donald Trump,’’ Warren said.

“Watch out,’’ she added. “He will crush you into the dirt to get whatever he wants.’’

Clinton, she said, has always been a fighter.

“She knows that you beat a bully not by tucking your tail between your legs and running but by standing your ground and fighting back,’’ Warren said.

Warren’s decision to back Clinton, which she announced almost three weeks ago, was long expected. Though she’s ideologically closer to Clinton’s primary opponent Bernie Sanders, she’s also a pragmatist and it’s been clear to party insiders for months that Sanders had no real path to the nomination.

But Warren and Clinton do have a fraught history — with Warren slamming Clinton over her vote in support of an industry-friendly overhaul to the nation’s bankruptcy laws. Warren wrote that Clinton voted with the large banks because she “couldn’t afford such a principled position.’’

It’s a theme that Republicans picked up on Monday.

“I don’t know how she can justify it, supporting the queen of Wall Street,’’ said Scott Brown, the former Massachusetts senator, in a conference call with reporters that was organized by the Republican National Committee. “I found her audition to be very uncomfortable.’’

Warren’s speech started heavy on her own autobiography — she weaved in references to her hardscrabble upbringing in Oklahoma, her three older brothers who have worked blue-collar jobs, and her rise from a graduate of a commuter college to high office.

“I’m the daughter of a maintenance man who made it all the way to the United States Senate,’’ Warren said. “And Hillary Clinton is the granddaughter of a factory worker who is going to make it all the way to the White House.’’

Clinton stood on the stage for Warren’s entire speech — an often awkward portion of these political events. But during the nearly 18-minute introduction Warren conveyed genuine enthusiasm for Clinton.

Clinton, in a nod to the liberal wing of the party that she just defeated, recounted Warren’s accomplishments.

“Some of the best TV since Elizabeth came to the Senate is actually on C-Span,’’ Clinton said, referencing viral videos of Warren taking on various banking interests.

“Whenever you see her pressing a bank executive or a regulator for answers, refusing to let them off the hook — remember she is speaking for every single American who is frustrated and fed up. She is speaking for all of us, and we thank her for that.’’

Clinton’s campaign infrastructure wasted no time disseminating the message. Guy Cecil, who is the cochairman of Priorities USA, one of Clinton’s super PACs, tweeted a photo of Clinton and Warren standing together at the event and wrote: “The stakes are high and Democrats are united. Love this picture.’’

Unlike others on the potential list of candidates for vice president, Warren has operated as a heat shield of sorts for Clinton, attracting some of the negative attention that Trump delights in showering on his opponents.

“I do just love to see how she gets under Donald Trump’s thin skin,’’ Clinton said, grinning.

That pattern continued on Monday, with Trump going on NBC to call Warren “racist’’ for making unsubstantiated claims of Native American ancestry.

Republicans have long accused her of fabricating her family history to boost her legal career. Warren has said that she never benefited from her lineage.

“She made up her heritage, which I think is racist,’’ Trump said on NBC. “I think she’s a racist actually, because what she did was very racist.’’

Brown, using the same talking points on the call with reporters, said that Warren “can take a DNA test’’ to clear up once and for all whether she has Native American blood.

Trump also continued to brand Warren as “goofy’’ — and employed the nickname again before Warren spoke on Monday.

From the stage, Warren shot back: “If you want to see goofy, look at him in his hat,’’ she said, a reference to Trump’s iconic red baseball hat emblazoned with the motto: “Make America Great Again.’’

Republicans were ready to attack the pair.

America Rising sent out a 2012 Boston Globe story that detailed some of Warren’s past legal work on behalf of large corporations, including her attempts to help LTV Steel fight a congressional requirement that it pay millions of dollars into a fund for its retired coal miners’ health care.

But those in the audience of 2,600 were energized after the event, with groups of friends eager to discuss the chemistry between the pair.

“You could tell they were really listening to each other,’’ said Amy Schardein, who came to the Cincinnati Museum Center at Union Terminal.

“It was nothing like Christie behind Trump,’’ said Jessy Griffith, referring to an uncomfortable moment in the 2016 campaign when New Jersey Governor Chris Christie stood behind Trump with a pained expression.

Ohio is one of only a handful of swing states — and recent polls show that Clinton and Trump are tied here. Two other potential vice presidential picks hail from Ohio: Senator Sherrod Brown and Representative Tim Ryan, whose district includes Youngstown.

Annie Linskey can be reached at annie.linskey@globe.com. Follow her on Twitter @annielinskey.