Baxter served in the Canadian Army and was the author of Historical Records of the New Brunswick Regiment, Royal Artillery, the unit he commanded from 1907 to 1912.

A Conservative Party member, he was elected to the 32nd New Brunswick Legislative Assembly in 1911.

He entered federal politics and served as Minister of Customs and Excise under Prime Minister Arthur Meighen in 1921 before taking over the leadership of the provincial Conservative party and leading it to victory in 1925.

Baxter was a leader of the Maritime Rights Movement which expressed the discontent felt by the maritime provinces concerning their loss of influence in the Canadian confederation dominated by the provinces of Quebec and Ontario.

He left politics in 1931 and was appointed Chief Justice of the New Brunswick Supreme Court in 1935, which he would serve for the remainder of his life.