In the spring of 1813 , he was appointed by Governor Caleb Strong to fill the U.S. Senate seat vacated by the resignation of Senator James Lloyd . He served from May 5 , 1813 to May 30 , 1816 , winning reelection to the seat in 1814 . He opposed the ongoing War of 1812 in these years , with his earlier diplomatic experience providing valuable knowledge to Federalist interests . He expressed approval of the 1814 Hartford Convention in which the New England states aired grievances concerning Republican governance of the country and the conduct of the war .