The label was used primarily by former supporters of the David Lloyd George-led coalition government, and most notably by Winston Churchill.
At the 1922 general election, in a number of constituencies local Unionist Associations decided to continue supporting National Liberal candidates and vice versa.
The term was meant to signify that the adherents believed in the principles of British constitutional government through electoral politics.
It was used to highlight their belief that Labour, as a socialist party, did not fully support the existing British constitution.
Any plans that Churchill may have had to create a Constitutionalist Party were shelved with the calling of another general election.