Gov. Kathleen Sebelius of Kansas is emerging as President Obama's top choice for secretary of health and human services, advisers said. Should she be nominated, Sebelius would bring eight years of experience as her state's insurance commissioner as well as six years as a governor running a state Medicaid program. But with President Obama about to begin a drive to expand health coverage, her strongest asset may be her record of navigating partisan politics as a Democrat in one of the country's most Republican states.