Dr. Mehmet Oz, President Donald Trump’s nominee to run the Centers for Medicare and Medicaid Services, endured nearly three hours of questioning from the Senate Finance Committee on Friday, with most of the questions focusing on Republican plans to reform Medicaid programs.

CMS is the largest payer for healthcare in the United States, covering more than 160 million through Medicare, Medicaid, the Children’s Health Insurance Program, and the Obamacare health insurance marketplace.