D.C. United is making a pitch to District officials to get in on the enthusiasm over soccer with a public-private partnership for improvements, such as a new roof at Audi Field. Danita Johnson, president of business operations for D.C. Committee of the Whole that soccer has become the “third-largest sport in the U.S. “As of now, we have doubled our sellouts with D.C. United over the past few years,” she said.