EXCLUSIVE, updated with Rhino Staging Northwest statement: IATSE’s ongoing labor dispute with Rhino Staging Northwest has spilled over to Michelle Obama’s book tour. The union is seeking to enlist the former First Lady in its efforts to win a contract with the company, a subcontractor that supplies riggers and stagehands to the Tacoma Dome, where she will be speaking on Friday to promote her best-selling memoir, Becoming. Jimmy Kimmel will join her onstage at the event.

“You may not be aware that a company, Rhino Staging Northwest, which has been engaged to staff your book talk in Washington State, has personnel policies and operations that are not consistent with the values you have represented throughout your career,” IATSE president Matt Loeb said in a letter to Obama last week (read it here). “We would like to ask you to consider using your platform to assist the men and women represented by the IATSE.

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“Rhino workers have regularly conducted audience outreach and ‘bannering’ outside the Tacoma Dome at recent concerts sponsored by Live Nation,” he told her. “If Rhino is used for your appearance you can expect that these actions will continue.”

“We would like to ask you to consider using your platform to assist the men and women represented by the IATSE,” Loeb wrote. “With your support, we hope to have the Becoming Book Tour Production sign a nation-wide agreement with the IATSE. A national agreement is what President Obama’s campaign signed with the IATSE in 2008 and 2012. We believe a nation-wide agreement could further protect workers at venues like the Houston Toyota Center. The agreement would cover all your venues and ensure all workers for your events have pension contributions, health care, and the highest safety measures in place.”

Tim Garnett, the attorney for Rhino Staging Northwest, issued a statement to Deadline today. “This is one of those things where they try to use the public as a means to put pressure on us,” he said, noting that he’s being negotiating with IATSE Seattle Local 15 over the past year. “We’re in the midst of negations for a first contract. We have both made contract proposals and we’re working though those proposals one by one.” Rhino, he said, has been a leader in the industry in terms of safety, and provides a health care and retirement program for qualified employees, most of whom, he said, are part-time.

Loeb, whose union endorsed Barack Obama in his two presidential campaigns, noted that. “While your husband was still President, Rhino workers tried to improve their working conditions by voting to form a union. The company refused to bargain, but eventually was ordered by the National Labor Relations Board to sit down with the workers and negotiate in good faith. Yet today, years later, Rhino continues to stall, workers’ health and safety issues persist, and compensation remains at a level below what it takes to support a family or even pay reasonable rent in the Seattle market.

“When you use the stage to talk to the audience about your journey from Chicago to Washington and your fight for fairness and for health care for those who have gone without,” he concluded, “my members will be backstage cheering you on. I intend to let them know that you are doing the same for them, fighting for the working men and women across this country.”

Deadline reached out to Michelle Obama and to Rhino but has yet to receive a comment.