Tom Perez, the labor secretary who is bidding to head the Democratic National Committee, received a crucial boost in 2013 when he was seeking Senate confirmation to be in President Obama’s Cabinet after the Maryland Chamber of Commerce wrote a letter endorsing him.

Perez was a controversial choice to be labor secretary. The letter, which was widely cited by Perez’s defenders to refute criticism against him, was part of a secret arrangement between Maryland Chamber President Kathleen Snyder and a close Perez ally, Scott R. Jensen. Jensen was assistant secretary at the Maryland Department of Labor, Licensing and Regulation, the agency that monitors state businesses and labor issues.