Republicans at the RNC signaled support for unions. Here's why experts are skeptical.

At the Republican National Convention this week, Teamsters President Sean O'Brien delivered the type of full-throated union advocacy that one would not expect at a gathering of top conservative officials.

"We are not beholden to anyone or any party," O'Brien, whose union boasts 1.3 million members, told the audience in Milwaukee, Wisconsin. "We want to know one thing: What are you doing to help American workers?"

The next day, vice presidential nominee JD Vance, a Republican senator from Ohio, indicated a second-term Trump administration would lend such a hand to labor. "We need a leader who's not in the pocket of big business but answers to the working man, union and non-union alike," Vance said.

Labor experts who spoke to ABC News expressed deep skepticism about the Republican gestures of support for unions.

The pro-labor message comes at a time when Republicans are eager to win over working-class voters, experts noted, saying the sentiment belies the party's record of policy positions that make it harder for workers to form unions and secure union contracts.

During his first term in office, Donald Trump weakened enforcement of federal labor regulations and appointed Supreme Court justices who issued rulings that limited union activity and worker protections, the experts said.

"Right now, both parties are in selling mode," Lynne Vincent, a professor of industrial and labor relations at Syracuse University, told ABC News. "I'm hesitant to give any power to those words, without serious commitment to policies that would support labor."

In a statement to ABC News, the Trump campaign said the former president would improve the financial conditions of union workers, especially in the auto industry.

"Union workers and all the nation's working families are paying the price for Crooked Joe Biden's failed economic policies. Joe Biden's radical electric vehicle mandate will destroy the livelihoods of countless U.S. autoworkers while sending the U.S. auto industry to China. President Trump will reverse Joe Biden's extreme electric vehicle mandate on Day One and save the U.S. auto industry for generations to come," Trump campaign National Press Secretary Karoline Leavitt said.

The Trump campaign has proposed an escalation of its tariff policy as a means of protecting U.S. businesses, thereby ensuring a robust job market and a bolstered domestic manufacturing industry.

"Trump wants jobs here in America. He wants things made in America," Stephen Moore, who served as an economic adviser to Trump, previously told ABC News.

Some Republicans have pointed to the selection of Vance as indication of a shift in the party, placing a priority on Vance's oft-expressed views critical of large corporations and sympathetic toward workers.

Sen. Josh Hawley, R-Mo., an ally of Vance, walked the picket line with members of the United Auto Workers during a strike last year.

Earlier this month the Republican Party platform released vows to "protect American workers." The party must "return to its roots as the Party of Industry, Manufacturing, Infrastructure, and Workers," the platform added. It does not mention the word "union."

Vance exemplifies a focus on symbolism over substance characteristic of Republican gestures in support of union workers, some experts said. The AFL-CIO, the nation's largest labor federation, gave Vance a 0% rating on its scorecard ranking elected officials' voting record for union-related issues. Hawley carries a rating of 11%, the AFL-CIO says.

"The selection of Vance as vice president did disturb the traditional corporate community that is at the core of the Republican Party," Erik Loomis, a labor professor at the University of Rhode Island and author of "A History of America in 10 Strikes," told ABC News. "But at the same time, neither Vance nor Hawley have supported a specific kind of legislation that helps labor unions."

In response to ABC News' request for comment, a press representative for Hawley pointed to an op-ed this week in which he backs bipartisan labor law reform. "Thousands of Americans have voted to unionize in elections but can never get a contract done, often due to corporate tricks," Hawley wrote in Compact. "How can we let that stand?"

ABC News has reached out to Vance's office for comment.

The speech from O'Brien drew praise from some labor leaders and criticism from many others. Randi Weingarten, president of the American Federation of Teachers, lauded O'Brien in a post on X. "Glad that he savaged big business for their greed," Weingarten said.

Among the critics was John Palmer, vice president at large of the Teamsters. "It is unconscionable for any Labor leader to lend an air of legitimacy to a candidate and a political party, neither of which can be said to have done or can be expected to do, anything to improve the lives of the workers we are pledged to represent," Palmer wrote in a column for the Las Vegas Sun.

O'Brien did not immediately respond to a request for comment.

When asked about O'Brien's speech, Rebecca Pringle, president of the 3-million member National Education Association, told ABC News: "It's everyone's right to speak their mind and for their organization."

Pringle added there should be no illusions about the Republican Party's posture toward organized labor. "What we have experienced with Donald Trump and the MAGA Republicans is that they don't care about workers and they don't support unions," she said.

Still, polling shows a large minority of union workers support Trump. Union households prefer Biden to Trump by a margin of 50-41, an NBC News survey in February found.

The labor embrace from some speakers at the RNC this week could help Trump and his allies increase that support, some experts said.

"They're trying to expand their white working-class base," Harry Katz, a professor of collective bargaining at Cornell University's School of Industrial and Labor Relations, told ABC News. "They're not idiots."