The ingredients of reform are clear: legalization for the 12 million, to yield bumper crops of new citizens, to make it easier to weed out criminals and to end the fear and hopelessness of life in the shadows; sensible enforcement at the border that focuses resources on fighting crime, drugs and violence; a strengthened employment system that punishes businesses that exploit illegal labor; and a future flow of workers that is attuned to the economy’s needs and fully protects workers’ rights.

The last point has been a sticky one with some unions. The agreement between the A.F.L.-C.I.O. and Change to Win — a rival federation that includes service employees, the Teamsters and carpenters — will center on a new approach to future immigration, a compromise in which an independent national commission calibrates the size of temporary-worker programs each year, based on conditions in labor markets. It may not be a perfect plan, but after years of vitriol, it’s encouraging to hear calmer voices outlining smart reform.