2010–2024: The Rhondda Cynon Taff County Borough electoral divisions of Cwm Clydach, Cymmer, Ferndale, Llwyn-y-pia, Maerdy, Pentre, Pen-y-graig, Porth, Tonypandy, Trealaw, Treherbert, Treorchy, Tylorstown, Ynyshir, and Ystrad.

[3] The constituency was formed following the Third Reform Act of 1884, as a result of the rapid growth of population in the two valleys over the previous twenty years.

During the 1880s the demand for working men representatives in the ranks of the Parliamentary Liberal Party were increasingly vociferous and there was a precedent for a Liberal-Labour (Lib-Lab) candidate in South Wales as Thomas Halliday had contested Merthyr Tydfil in 1874.

The local trade union, the Rhondda Steam Coal Miners' Association, laid claim to the candidacy as early as 1883, on the basis that the franchise had been extended to many working men within the county constituencies and that in Mabon, their agent for six years they had the ideal candidate.

[4] The local Liberal Association, however, formed in early 1885,was dominated by middle-class business and professional men, and included a disproportionate number of colliery officials.

[5] At a meeting in April 1885 six names were put forward as possible candidates for the nomination, including Lewis Davis, Mabon and Alfred Thomas, a leading figure in the municipal life of Cardiff.

[5] Shortly afterwards, Lewis Davis was invited by the Association to be its parliamentary candidate and defeated Mabon in a ballot by 143 votes to 51.

[4] The refusal of the trade union movement to accept this decision and to support an independent campaign by Mabon is regarded as an important watershed in the political history of South Wales.

Mabon's adherents, in turn, claimed that the miners' had held mass meetings throughout the two valleys to promote his candidature long before the middle-class-dominated Association was established.