Cynon Valley (previously Aberdare) has returned Labour candidates to Westminster since 1922 and rivals have in the past made little impact in general elections. In 1997, Ann Clwyd secured nearly 70% of the vote. Second placed Plaid Cymru trailed far behind, with only 10.6%.
Despite this, in the 1999 Welsh Assembly elections Plaid Cymru came within 677 votes of victory. Plaid has also made dramatic advances at local government level, winning 13 out of 21 wards in the constituency.
Cynon Valley is a former mining area and is home to the last deep mine in Wales, worker-owned Tower colliery. Like many south Wales communities of this kind, despite having attracted new industries, it still has relatively high levels of unemployment and social deprivation.