He first stood for Parliament at the 1918 general election, when Pontypridd was won by the Coalition Liberal candidate Thomas Lewis. Lewis was forced to seek re-election in July 1922 when he was appointed as a Lord Commissioner of the Treasury (a nominal post held by a government whip), and the by-election was won by a new Labour candidate, Thomas Jones.
Jones held the seat for nine years until he resigned from the House of Commons on 4 February 1931. Davies was the Labour candidate in the resulting by-election, which he won 60% of the votes. He held the seat for a further seven years, until his death in November 1937, aged 64.
- Leigh Rayment's Historical List of MPs – Constituencies beginning with "P" (part 2)
- Department of Information Services (9 June 2009). "Appointments to the Chiltern Hundreds and Manor of Northstead Stewardships since 1850" (PDF). House of Commons Library. Archived from the original (PDF) on 6 February 2011. Retrieved 30 November 2009.
- Craig, F. W. S. (1983) . British parliamentary election results 1918–1949 (3rd ed.). Chichester: Parliamentary Research Services. p. 562. ISBN 0-900178-06-X.
- Hansard 1803–2005: contributions in Parliament by David Lewis Davies