Dr. Shah, who spent most of his career in the Midwest, came to Maine in 2019, when Gov. Janet Mills hired him as the state’s public health director. He has campaigned as an outsider, promising to bring fresh perspective, as he competes against three former state legislators.
The three, all of whom are advancing to the runoff, are Shenna Bellows, Maine’s secretary of state; Troy Jackson, a logger from northern Maine and former State Senate president; and Hannah Pingree, a former State House speaker who went on to work for the Mills administration. They campaigned as progressives and formed an alliance last month, asking voters to rank them in the top three spots in an apparent effort to box out Dr. Shah.
Ms. Pingree, the daughter of U.S. Representative Chellie Pingree, was in second place on Wednesday morning, with 23 percent of the vote. She received the endorsement of Ms. Mills.
Angus King III, the son of Senator Angus King, finished last, and will not advance to the runoff.
Mr. Charles was consistently the front-runner in a crowded Republican field made up mostly of business leaders, where his closest competitors were Jonathan Bush, a cousin of President George W. Bush, and Benjamin Midgley, a former president of Planet Fitness. Also running were Owen McCarthy, a health care entrepreneur and son of a logger from northern Maine; Garrett Mason, a former State Senate majority leader; David Jones, a real estate broker, and Robert Wessels, a small-business owner.
Mr. Midgley and Mr. Bush each had 20 percent of the vote on Wednesday morning and will advance to the runoff, as will Mr. Mason, Mr. McCarthy and Mr. Jones.