Flemming was a school teacher and lumberman before entering politics and serving as Provincial Secretary-Treasurer from 1908 to 1911 and Minister of Lands and Mines from 1911 to 1914.

In the June 1912 general election, Flemming led his provincial party to the biggest electoral victory in its history.

In 1914, Premier Flemming was forced to resign after charges of fundraising irregularities against him were made public by a powerful group of back-room Liberals known as the "Dark Lantern Brigade" led by party organizers Peter Veniot and Edward S. Carter plus lawyer and Federal Member of Parliament, Frank Carvell.

His son, Hugh John Flemming took over the business and too entered politics, serving as Premier of New Brunswick from 1952 to 1960.

James Kidd Flemming suffered from poor health for many of his adult years and died in 1927 at age fifty-eight.