Deering, a Democrat, served in the Maine House of Representatives from one term (1910-1912). He also served four terms as chairman (de facto mayor) of the Portland, Maine City Council in 1924, 1927, 1934 and 1935. Deering served on the State Highway Commission for seven years, including a year as Chair.
In 1923, Portland voters dramatically altered the city charter, which included eliminated the previously elected mayor position and by cutting the number of City Councilors from 18 common council members and 9 alderman to 5 at-large members.
The election was heavily supported by "native" residents from the previous neighborhoods of Deering, Maine. Deering was elected subsequently elected in a citywide as the top vote-getter.
The new council chose as the first chairman of the City Council, which he held twice during his first term in office. Leaving office in 1928, he was elected again in 1932.
During his 5 year term which ended in December 1937, he again served twice as Council chairman
He left office less than a month prior to his death. Deering had an intestinal disease and died in December 1935 at Peter Bent Brigham Hospital in Boston, Massachusetts.