Complex sentence: He had originally sought the backing of the local Unionist association, which happened to be called the Westminster Abbey Constitutional Association, and adopted the term'Constitutionalist' to describe himself during the by-election campaign.
Split into simpler sentences: 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.