Three years after President Obama signed his signature healthcare law, his administration is facing big challenges to make sure it works.

Health and Human Services Secretary Kathleen Sebelius spent the past week touting the law’s benefits ahead of its third anniversary on Saturday. But HHS still faces a steep climb to fully implement the law — and sell it to a skeptical public.

HHS officials say they absolutely will meet the biggest and most imposing deadline — having new insurance exchanges up and running in 27 states by Oct. 1, to begin enrolling people in coverage that will take effect Jan. 1.