Leaning into friendlier political terrain, a union for Minnesota nurses renewed its call Wednesday for state lawmakers to establish requirements that would dictate how hospitals staff their emergency rooms, childbirth wards and other units. The drive to impose minimum staffing levels in law has the union and hospitals bracing for a contentious fight, one that could also expose simmering divides between nurses who are represented by the Minnesota Nurses Association and those who are not. Minnesota would join California as the only states with such a law if new Democratic majorities and Gov. Mark Dayton go along.