Lindsay Whittle, the Plaid candidate, is no stranger to elections.
He has stood in ten general elections and every devolved election for over a quarter of a century – and victory has remained elusive.
He has been a local councillor for nearly 50 years.
Whittle reckons that when it comes to what appears to be a cratering in support for Labour, he has never seen anything like it.
He is buoyant and thinks that in a tight tussle with Reform UK, he can squeak a win.
Plaid are allowing themselves to dream, with some supportive polling evidence, external right now at least, that they could be running the Welsh government after next May’s devolved elections across Wales. They see Reform as their big opponent.
But some of Labour’s opponents fret that they may be under pricing what they fear could be a new phenomenon – what one figure described to me as “shy Labour voters.”
Some people might be unwilling to admit it, or saying they are undecided, but could they plump for Labour in the end? Let’s see.
The Welsh Conservatives, in a part of the world rarely fertile for them, find themselves cropped further out of the picture, again courtesy of Reform.
Perhaps little wonder when former Conservative cabinet minister Sir Jacob Rees Mogg is suggesting Tory voters in Caerphilly should consider voting Reform, external to prevent Plaid from winning.
Incidentally, he also suggests Labour supporters should back Reform too, for the same reason.
Both of Westminster’s giants – Conservatives and Labour – are feeling squeezed here.
The Liberal Democrats, the Green Party and others are vying for support too.
You can see a full list of the candidates standing in the by election here.
As I say, next May, there will be elections across Wales to the Welsh Parliament, the Senedd.
By Friday morning here, we could be seeing the first big indicator of a seismic change to come.
