Vermont Senator Bernie Sanders and others are mocking President Trump after Trump told a room full of state governors that “nobody knew” replacing the Affordable Care Act would be “so complicated.”

President Donald Trump: “Now, I have to tell you, it’s an unbelievably complex subject. Nobody knew that healthcare could be so complicated.”

Senator Sanders responded to Trump’s comments during an interview with CNN’s Anderson Cooper.

Sen. Bernie Sanders: “Well, some of us who were sitting on the Health Education Committee, who went to meeting after meeting after meeting, who heard from dozens of people, who spent—stayed up night after night trying to figure out this thing, yeah, we got a clue. When you provide healthcare in a nation of 320 million people, yeah, it is very, very complicated.”