Vice President Kamala Harris and Minnesota Gov. Tim Walz are rallying voters across the Midwest this week, looking to build on support from key union leaders as they promote a message of pro-labor policies that they say benefit the middle class.

At the leadership level, the Democratic ticket’s been deemed a clear choice. Shawn Fain, the president of the United Auto Workers who endorsed Harris last week and appeared alongside the pair Tuesday, called them a “Democratic Dynamic Duo.”

The public show of support follows weeks of behind-the-scenes maneuvering to renew support from the unions that had backed President Joe Biden, who called himself the most pro-union president in history, until he made a surprise exit from the race last month.

Since then, Harris has set out to prove that she won’t veer from Biden’s agenda — working the phones with union leaders, holding early campaign events alongside the American Federation of Teachers and the UAW, and notching the endorsement from a major hospitality union, despite a proposal by former President Donald Trump to increase service workers’ take-home pay.

And the selection of Walz as the ticket’s No. 2 is seen as bolstering those labor bona fides: Walz and his wife were both union members, and his tenure as governor includes infrastructure, climate and paid leave legislation.

“It’s very much the Biden agenda in a state where you can actually legislate an agenda,” Seth Harris, Biden’s former labor policy adviser at the National Economic Council, told CNN about Walz’s record in Minnesota. “It very much parallels what they did at the federal level.”

The union leaders who back Biden — and now Harris’ — agenda wield an immense amount of power within the Democratic Party, and the work is just beginning to try to turn their endorsements into member turnout in November. One influential union — the International Brotherhood of Teamsters, which represents a diverse set of industries — may remain neutral this cycle, withholding an endorsement of the Democratic Party candidate for the first time in nearly three decades.

But beneath the executive level, work remains to shore up support among millions of card-carrying union members who represent a critical constituency for both parties across the manufacturing-heavy Midwest — and whose political allegiances often don’t mirror those of their leadership.

In a memo released Thursday, the Harris-Walz campaign said it plans to spend “hundreds of millions of dollars” throughout the fall to reach an estimated 2.7 million union members in battleground states.

“That means something when roughly 45,000 votes in key states decided the election four years ago,” campaign manager Julie Chavez Rodriguez wrote in the memo.

Endorsements and the everyman

The abrupt change in Democratic candidates sent unions scrambling to adjust their messaging internally — to print new signs, film new ads explaining the policies their new candidate would support, and update talking points for local chapters.

Part of the task at hand, one top AFL-CIO executive told CNN, is connecting the infrastructure and semiconductor laws that Biden and Harris enacted to the economic boon felt in various industries.

“There’s so much work available, and they’re trying to bring in more apprentices, get more people trained up because of these investments,” said Greg Regan, the president of the Transportation Trades Department at the AFL-CIO. “This is not surface-level stuff.”

While that messaging may take time, many rank-and-file workers are not sold.

A video message from Fain praising Walz on the union’s Facebook page elicited a tsunami of negative comments from factory workers across the country, many of whom voiced their support for the Republican ticket.

Harris and Walz are set to meet with the UAW members at a local union hall in the Detroit area on Thursday afternoon. The more intimate setting than other campaign events, featuring about 100 rank-and-file UAW members, was planned to connect with the workers and try to mobilize support beyond the union’s leadership.

Divergent views are expected in an organization representing roughly 400,000 active employees and nearly 600,000 retired workers. But it illustrates that many voters still see the actions of the Biden-Harris administration as not going far enough.

In September, Biden joined a picket line and called for higher wages when the union was locked in contentious talks with the Big Three automakers. Shortly after an agreement was reached to break the strike, UAW’s Fain endorsed Biden.

Biden and his labor secretary also got involved to broker a truce between a dozen railroad industry unions — including the International Brotherhood of Electrical Workers — who were threatening a strike in 2022. Biden praised the deal as a compromise at the time, even as workers simmered over some of the terms in the weeks that followed.

And some of that anger remains. A Facebook post by IBEW promoting Walz joining the ticket received more than 800 comments, some favorable but most decrying the economy and the plights of workers over the last three and a half years. Among those opposing the IBEW’s endorsement, many suggested that the union’s leadership was out of touch with its members.

Labor groups conduct their own internal polling to gauge the views of their members and what messages will be most effective. Those polls may show a more fractured base than the near-unanimous endorsements would suggest.

“I expect some data toward the end of the month, especially after the (Democratic National) Convention,” Regan of the AFL-CIO told CNN. “It will be really interesting to see.”

Teamsters’ decision looms

The International Brotherhood of Teamsters, a union with 1.3 million members, is also polling its rank-and-file members for their views and is expected to decide after the convention whether it will endorse either candidate for president.

Shortly after Harris became the presumptive Democratic nominee, Teamsters leadership invited her to participate in a roundtable interview on top issues facing the union.

“Teamster members want to hear your vision on issues that affect their families,” said the letter to Harris, obtained by CNN.

The roundtable would focus on four issues, according to the letter: the shrinking American middle class; corporate bankruptcy reform; antitrust enforcement in the warehouse and package delivery industries; and the freedom to form and join a union.

A Teamsters spokesperson told CNN that Harris has not responded to the invitation. The Harris campaign did not answer questions about the invitation.

Top Democrats have expressed frustration with Teamsters president, Sean O’Brien, for delivering a primetime speech at the Republican National Convention while still seeking a speaking role at the Democrats’ event. A convention official said no final programming decisions have been made.

“He’s got a lot of members who support Trump, a lot who support Harris, and a great deal on the line from a policy perspective,” said Seth Harris, the former Biden labor adviser. “The endorsement shouldn’t be decided by who speaks at the convention.”

DNC officials, according to people with knowledge of the conversations, have been weighing the Teamsters request, while also considering a desire to recognize labor leaders who have not wavered in their loyalty to the party.

“The list of union leaders who want to speak at the DNC is pages long,” Harris said. “The DNC has a difficult choice to make.”

A spokesperson for O’Brien said he requested speaking roles at both parties’ conventions. In response, Trump invited O’Brien personally to the Milwaukee event, the spokesperson said. The DNC, she said, has not responded.