But what of the advocacy groups that work under none of the party's constraints -- groups the administration is counting on to play the kind of public hardball with individual lawmakers that it cannot? Already, MoveOn.org and the Service Employees International Union have run commercials attacking some Democratic senators for pushing compromises that would undermine a universal plan. Such ploys can be helpful in the legislative back-and-forth -- no small thing. But they are no substitute for campaigns to build the one thing that would ensure enactment of such a plan -- a mass movement. They are the fruits of a legislative strategy, not a movement-building strategy.