Forced into an uneasy balancing act between their members and the president they helped elect, the national teachers' unions are responding to the Obama administration's teacher-effectiveness agenda in notably different ways. Publicly at least, National Education Association President Dennis Van Roekel has hewed closely to the union's internal policy statements on such matters as embedding student learning into policies on teacher evaluation and pay. But the heads of the 3.2 million-member NEA's state affiliates have taken sundry positions on initiatives such as the federal Race to the Top competition, with some participating in their states' bids for the $4 billion initiative and others opposing them outright. In contrast, the president of the 1.5 million-member American Federation of Teachers, Randi Weingarten, has laid out--and helped local affiliates adopt--an explicit agenda for her union that, for example, endorses a new approach to teacher evaluations, including the consideration of test scores alongside other factors. Those responses, say experts on teachers' unions, are a complex product molded significantly by the unions' respective governance structures. Among other differences, the structures make the national bully pulpit a more powerful place at the AFT, but tilt NEA policy away from its president and toward its state affiliates. The author reports on how unions' tactics diverge in engaging the Obama administration's teacher-effectiveness agenda.