President Obama nominated Dr. Vivek H. Murthy, an early supporter and grass-roots advocate for the Affordable Care Act, as surgeon general on Thursday. Dr. Murthy, 36, is a founder and the president of Doctors for America, a group that campaigned for the health care law before Congress passed it in 2010. He is a doctor at Brigham and Women's Hospital in Boston and an instructor at Harvard Medical School. Last year, he was the co-author of an article for The New Republic responding to criticism of the health care law and citing its support among doctors, although it acknowledged qualms among them.