The seat dates to the earliest century of regular parliaments, in 1295; its double representation was halved in 1885, then being altered by the later-termed Fourth Reform Act in 1918 (the first being in 1832).
Between an election of 1910 when the seat leant to the left matching the national result and June 2017, the seat elected a Conservative. Canterbury is the only seat won (held or gained) by a Labour candidate in 2017 from a total of 17 in Kent. Duffield's 2017 win was one of 30 net gains of the Labour Party.
The widened Canterbury constituency was formed from an expansion of the narrow parliamentary borough (or simply borough) of the same name that existed from 1295 to 1918. This had elected two MPs from 1295 (the Model Parliament) until 1885, and then one until 1918.
From 1835 (where a Conservative was elected on petition) until 2017, the local electorate elected candidates of the Conservative Party (with the exception of the election of Independent UnionistFrancis Bennett-Goldney, MP from 1910–18); the seat was recognised in the Guinness Book of World Records as the longest uninterrupted period of one party holding a Parliamentary seat. The election of Labour's Rosie Duffield, who won the seat by just 187 votes in the 2017 election, marked the end of a 185-year period of Canterbury always electing Conservative-allied MPs, the longest recorded broken record for party representation in British political history.
1918–1950: The County Borough of Canterbury, the Urban Districts of Herne Bay and Whitstable, the Rural Districts of Bridge and Elham, and the Rural District of Blean with the detached parts of the civil parishes of Dunkirk and Hernhill which were wholly surrounded by the rural district.
1950–1983: The County Borough of Canterbury, the Urban Districts of Herne Bay and Whitstable, and the Rural District of Bridge Blean.
1983–1997: The City of Canterbury wards of Barham Downs, Barton, Blean Forest, Chartham, Chestfield, Gorrell, Harbledown, Harbour, Little Stour, Marshside, Northgate, North Nailbourne, St Stephen's, Seasalter, Stone Street, Sturry North, Sturry South, Swalecliffe, Tankerton, Westgate, and Wincheap, and the Borough of Swale wards of Boughton and Courtenay.
1997–2010: as above but with the wards of Boughton and Courtenay removed.
2010–present: The City of Canterbury wards of Barham Downs, Barton, Blean Forest, Chartham and Stone Street, Chestfield and Swalecliffe, Gorrell, Harbledown, Harbour, Little Stour, North Nailbourne, Northgate, St Stephen's, Seasalter, Sturry North, Sturry South, Tankerton, Westgate, and Wincheap.
Canterbury constituency comprises the larger part of the City of Canterbury District, containing the city and surrounding villages, together with the coastal town of Whitstable, but excluding the town of Herne Bay which is in the North Thanet constituency (although it was in this seat before the 1983 redistribution). The wards containing the smaller rural villages are mostly Conservative, but Labour saw strong support in 2017 in Canterbury itself and Whitstable.
Another General Election was required to take place before the end of 1915. The political parties had been making preparations for an election to take place and by July 1914, the following candidates had been selected;
Smythe retired before polling. The election was declared void on petition, due to bribery, and the writ suspended on 21 February 1853. A by-election was called to replace both MPs in August 1854.