As health care policy battles rage in Washington, Andrea Walsh is preparing for her first full year as chief executive at HealthPartners. An attorney who joined the company in 1994, Walsh accepted the leadership handoff from longtime CEO Mary Brainerd. But Walsh may face more difficult financial challenges. Politicians, employers and consumers are decrying the high cost of health care and insurance premiums. HealthPartners plays a dual role as an operator of hospitals and clinics and as an insurance provider. The nonprofit serves more than 1.8 million people through its health plan.