In the first days of his campaign for the Democratic presidential nomination, former Vice President Joe Biden has pursued support from unions with the confidence of a man who has defined his political life by his singular closeness with organized labor.

“I make no apologies: I am a union man, period,” Biden said at his kickoff rally at at the Teamsters Local 249 in Pittsburgh on Monday afternoon, to an audience largely composed of union workers. “The country wasn't built by Wall Street bankers, CEOs and hedge fund managers—it was built by you. It was built by the great American middle class, and the American middle class was built by you, by unions!”

But Biden’s bid to build a strong coalition of union supporters in the primary and beyond has, so far, frequently been focused on largely white, largely male career fields and labor organizations—electricians, firefighters, Teamsters—rather than the nation’s increasingly diverse unionized workforces.

“Those of us who work in and around the labor movement understand how diverse the membership is. The old stereotypical view of white male-dominated unions is a thing of the past,” Steve Rosenthal, former political director for the AFL-CIO, told The Daily Beast. “It’s one element of the labor movement, but not even the dominant element anymore. With the growth of the public and service sectors, with organizing, the bigger unions like [National Education Association] NEA, [American Federation of State, County and Municipal Employees] AFSCME and [Service Employees International Union] SEIU have incredibly diverse memberships.”

Some of Biden’s off-the-cuff remarks in front of such audiences—joking about consensual touching in front of one mostly male audience of electrical workers to make light of accusations that he has made women feel uncomfortable—also give the impression that he sees unions as a boys’ club. But the makeup and political ideology of unions is no longer so synonymous with that of white working-class men.

“Forty years ago, women were trying to work on job sites in New York City, and weren’t able to do it, and unions were an obstacle to that. Forty years later, they’re our strongest partner,” said Amanda Kogut, vice president of programs at Nontraditional Employment for Women (NEW), a nonprofit that prepares, trains, and places women in careers in the skilled construction, utility, and maintenance trades.

“Folks have an idea in their mind who labor is, who a tradesperson is—probably a middle aged white man,” Kogut said. “But labor represents and fights for the rights of a broad and diverse group of people—labor is really there to be the champion for them all, and when you think about it in that context, they represent the worker today.”

Like the term “working class,” which when employed by talking heads is a term that almost always means the white working class, the image that comes to mind when politicians reach out to labor unions is almost always male, Caucasian, and, as Biden listed during a speech before an electrical workers union conference last month, are “ironworkers, steelworkers, boilermakers, plumbers, electrical workers.”

But even Biden’s own support is more diverse than the crowds to whom he’s made his earliest pitch, more closely resembling the crowd of UFCW workers he addressed at a Stop & Shop strike days before announcing his run. Early polling has shown that the former vice president is performing well among non-white Democrats—according to a Quinnipiac University poll released on Tuesday, Biden actually performs better among non-white voters (42 percent) than white voters (35 percent).

Biden’s early focus on certain types of unions risk giving the impression that he’s more interested in winning back working white males from President Donald Trump than advocating for policies that can build a coalition of diverse union support.

Trump, for one, clearly feels that Biden’s entreaties to organized labor is code for a bid for his base. Following the endorsement of the former vice president’s candidacy by the International Association of Fire Fighters, Trump complained that while he’ll “never get the support of Dues Crazy union leadership,” the rank-and-file members of those unions “love Trump.”

“The Dues Sucking firefighters leadership will always support Democrats, even though the membership wants me,” Trump tweeted. “Some things never change!”

The next day, Trump retweeted nearly 60 people who said that the firefighters in their lives would not support Biden over Trump.

Trump may not be wrong. White, male union members being tempted to vote for social identity over their economic interest “is an old problem and an old argument” in political labor history, said Professor Jefferson Cowie, a social and political historian at Vanderbilt University whose research focuses on inequality and labor shape American politics.

“Going back to Nixon, who had a white, male, blue-collar strategy to win the hearts of white male industrial workers out from underneath the AFL-CIO leadership, there’s always been a strong constituency that’s going to vote whiteness and maleness.”

These “Bruce Springsteen voters,” as Eric Alterman dubbed them, form a strong constituency in labor circles that “votes things other than its economic interest,” Cowie said. “Biden’s project is going to be trying to reach out beyond his white male blue-collar base… the whole thing’s built on coalitions.”

The strength of that coalition is far from the guarantee it once was. Between 1978 and 2017, union membership in the United States fell from 26 percent of the workforce to 10.7 percent, according to the Bureau of Labor Statistics, and the Democratic share of that cohort has fallen as well. Among union voters, Hillary Clinton outperformed Trump by 8 percentage points nationally, the smallest margin for a Democrat since 1984, when Walter Mondale actually lost labor voters to President Ronald Reagan. By comparison, President Barack Obama carried union voters in 2012 by 18 points.

Clinton’s relatively poor performance may give credence to Trump’s argument that the endorsement of union leadership is no guarantee that union members will fall in line. According to the AFL-CIO, the largest federation of unions in the United States, 37 percent of members supported Trump in 2016, a 4-point increase from 2012.

The drop in union membership, Cowie said, may have actually contributed to increased union support for Trump, a plutocrat who frequently chose to use non-union workers on construction projects, and famously flaked on paying the laborers he did employ.

“Trump is an expression of so many people feeling left out,” Cowie said, calling Trump’s resonant attacks on diversity and immigrant labor part of a trend in labor history going back to the fraught relationship between unions and social progressives in the 1970s.

“In a lot of ways, that was the moment when white working class guys who were the center of the labor movement in the ’60s and ’70s sort of took the whole thing down with them, in a way,” Cowie said. “By the early ’80s, you begin to see the precipitous decline of the institutional strength of organized labor.”

Judging by Biden’s nascent stump speech, the former vice president sees tapping into that resentment as a useful tool to shore up union support.

“We’ve gotten so damn sophisticated. We’ve gotten so damn elitist,” Biden said in a speech before electrical workers in April. “How the hell did we get to a place where a lot of you don’t think the rest of the country sees you, or hears you, or knows you, or maybe most importantly, respects you?”

But despite such direct appeals, with a wealth of possible options at their disposal, the labor movement has indicated that it will take its time considering all the candidates and where they stand on key issues before making any kind of endorsements in the Democratic primary.

“This is why we have a primary process, which we are in the beginning stages of now,” Randi Weingarten, president of the American Federation of Teachers, told The Daily Beast. “The Democratic primary voters—young and not so young; male, female and nonbinary; and people of all religions, races and geographic areas of the country—will give Joe, Bernie, Elizabeth, Kamala, Pete, Amy, Beto and the other 2020 Democratic candidates a full hearing.”

“I think we will have to see over time if in fact the former vice president was attempting to appeal to that certain segment of the labor movement with the images that were being projected,” Rosenthal said. “But certainly what he was saying has appeal across the movement.”

But Biden’s own record may complicate his outreach on that front. As a senator, Biden supported the North American Free Trade Agreement, and backed the Trans-Pacific Partnership as vice president, both trade deals that have been opposed by unions and bashed by Trump. Biden’s late entry into the Democratic primaries has also left Biden’s campaign cash poor, which means getting donations from union-busting groups and individuals—starting on the very day he announced his campaign.

According to an early donor list mistakenly attached to a invitation to Biden’s first fundraiser in Philadelphia on April 25, the event raised tens of thousands of dollars from employees and family members of attorneys at the law firm Cozen O’Connor. The firm specializes in labor disputes, including helping employers “prepare for and respond to picket lines, strikes, lockouts, and other economic campaigns,” as well as to “avoid unionization through positive employee relations.” Cozen O’Connor’s website notes that the firm’s attorneys “manage labor relations with a clear eye toward the bottom line.”

Of the $70,150 that had been pledged to Biden’s campaign at the time the list was released, $46,850 came from checks signed by Cozen O’Connor employees and their family members.

Told of that donor breakdown, Joe Dinkin, national campaigns director of the progressive Working Families Party, was not pleased.

“Biden stood next to a union and then stood next to a union-buster,” Dinkin told The Daily Beast. “You know, we have a song, ‘Which Side Are You On,’ and Joe Biden’s going to have to choose.”

The historically diverse field of Democratic contenders may also pose some challenges for Biden’s attempts to line up labor support.

“The labor movement is diverse—it’s not just full of guys in hard hats. It’s also full of women and people of color, especially in the growing service sector unions,” Dinkin said. “If Joe Biden wants their support, he’ll need to explain his record and talk about how his policies will improve their lives inside and outside the workforce.”

Biden’s campaign told The Daily Beast that the former vice president has been a staunch ally of labor for decades.

“Vice President Biden has stood with organized labor his whole career,” said national press secretary T.J. Ducklo. “As he’s said all week, he believes this country was built by labor, by the American middle class, but too many families are being left out. He’s running for president to restore the basic bargain that used to exist in this country where when you work hard, you were able to share in the prosperity your work helped create.”

Union leaders told The Daily Beast that they’re not inordinately concerned about Biden’s past support for trade deals.

“Anyone who knows Joe Biden—in fact, even people who don’t know Joe Biden—knows this: Joe Biden cares about people,” Weingarten said. “Joe Biden cares if your kid is sick, if you’ve lost your job, if you’ve been preyed upon on a college campus, if your aging parents are hanging in there… That is fundamentally who he is.”

But human dignity, Kogut noted, extends far beyond labor relations—and union workers, particularly women and minorities, will be searching for a candidate who can strengthen dignity in all areas of their life.

“For us, that’s somebody who has a really strong stance on equity in the workforce—somebody who has a really strong stance on women in the workforce and safety of women in society,” Kogut said. “The concerns of labor are really the concerns of everybody, so having access to healthcare, having access to a safe place to work, being able to invest in yourself and your family... Those values reflect everybody’s values.”