Following is the Dec. 20 statement from Senator Angus King in response to Mattis’s resignation:

When I first considered General Mattis’s nomination to serve as Defense Secretary, I concluded that he was an experienced leader who would serve as a moderating voice within the Administration. After nearly two years of service, I can say with confidence that Secretary Mattis has filled this role to the best of his ability given the Administration in which he served, providing a seasoned, rational voice on national security in the midst of numerous international challenges. His departure is extremely worrisome, particularly as it comes on the heels of a number of increasingly erratic foreign policy decisions that endanger American interests abroad and undermine our nation’s place as a world leader.

Quite frankly, I’ve slept better knowing that Secretary Mattis was leading the Department of Defense and providing counsel to this President on issues of national security, and while I understand his reluctance to continue to serve in an administration that ignores his expertise, I’m unsure who — if anyone — will be able to replace his measured, thoughtful approach in these important conversations. The loss of Jim Mattis’s voice is a loss for the American people. He will leave mighty shoes to fill, and I will measure any nominee the President puts forward against Secretary Mattis’s distinguished record of performance, patriotism, and service to his country.