Constitutionalist was a label used by some British politicians standing for parliament in the 1920s, instead of the more traditional party labels. The label was used primarily by former supporters of the David Lloyd George led Coalition Government, and most notably by Winston Churchill. However, there was no actual party called the Constitutionalist Party.
In 1922 when the Unionist Party voted to end the Coalition Government with the National Liberal Party there were still members of both parties who preferred to continue working together. At the 1922 General Election in a number of constituencies local Unionist Associations decided to continue supporting National Liberal candidates and vice versa. However, by the 1923 General Election the National Liberals had formally re-joined the Liberal Party. In some constituencies there was still some electoral co-operation between Unionists and Liberals. In Dartford a former National Liberal MP, George Jarrett chose not to join the Liberal party and sought re-election as a 'Constitutionalist'. He was supported by the local Unionist Association.
The term had nothing to do with Constitutionalism in the philosophical sense. 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 the Labour Party as a socialist party, did not fully support the existing British Constitution. In January 1924 the first Labour Government had taken office amongst fears of threats to the Constitution.
The former National Liberal Cabinet Minister, Winston Churchill was an adherent to this view of Constitutionalism. He was noted at the time for being particularly hostile to socialism. In March 1924 Churchill sought election at the Westminster Abbey by-election, 1924. He had originally sought the backing of the local Unionist association which happened to be called the Westminster Abbey Constitutional Association. He adopted the term 'Constitutionalist' to describe himself during the by-election campaign. After the by-election Churchill continued to use the term and talked about setting up a Constitutionalist Party.