“Sold!” yelled John Gay, a lobbyist for the American Hotel and Lodging Association. Mr. Sharry quickly added that the deal must include advocacy for “three little, tiny pieces of paper: a green card, a union card and a voter registration card” for unauthorized immigrants.

For me, a reporter who had long covered immigration in the Southwest and Mexico, the exchange was a revelation about the politics of immigration in Washington. Business lobbyists like Mr. Gay — conservatives who seek loose labor markets so employers can keep wages down — align themselves with liberal activists like Frank Sharry to pursue policies that serve their groups.

Who, I wondered, was lobbying for the American workers competing with the new arrivals? The answer, I learned, was no one. As the former labor secretary Robert Reich once put it, “There’s no National Association of Working Poor.”