Historicaly the Cynon Valley has been a Westminster and Senedd Constituency as well as having its own Borough Council before being merged into RCT.
It is covered by two Plaid Cymru constituency committees - Merthyr Aberdare and Pontypridd. With everything 'above' Mountain Ash being in Aberdare Merthyr Constituency and 'below' in Pontypridd Constituency .
You can see what Plaid is doing in:
Merthyr Aberdare Constituency on their Facebook Page by clicking here
Pontypridd Constituency on their Facebook by clicking here
or more generally in the Cynon Valley by clicking here