U.S. Health and Human Services Secretary Kathleen Sebelius asked a group representing nearly 46,000 physician assistants on Tuesday to help persuade uninsured Americans to sign up for coverage under President Barack Obama’s healthcare reform law.

As part of a politically embattled administration effort to rally support for the landmark reform law, Sebelius appealed to physician assistants as care providers who treat large numbers of people with little or no health insurance, including those in Republican-controlled states that have rejected the 2010 Patient Protection and Affordable Care Act.

Sebelius, Obama’s top healthcare adviser, has run into mounting opposition from Republicans over efforts to marshal private sector support for a public outreach campaign that could determine whether Obama’s signature domestic policy achievement succeeds or flops, just as the 2014 midterm election campaign gets under way.