Welsh Labour politician Hefin David has died suddenly, aged 47.
Mr David had been Member of the Senedd (MS) for Caerphilly since 2016.
Paying tribute, First Minister and Welsh Labour leader Eluned Morgan called him an "outstanding politician" who would be "greatly missed".
Gwent Police said a 47-year-old man was found unresponsive at a property in Nelson, Caerphilly county, on Tuesday evening, and the death was not being treated as suspicious.
His partner was Cynon Valley MS Vikki Howells, the minister for further and higher education in the Welsh Labour government.
The first minister said: "We are extremely saddened by the sudden death of Hefin. Our thoughts are with his family at this terrible time.
"Hefin was a much-loved member of the Labour family. He served Caerphilly as a councillor and a Member of the Senedd with pride and passion.
"He was an outstanding politician, warm and enthusiastic and a great communicator – especially on behalf of his constituents.
"He will be greatly missed."
Mark Hobrough, Gwent Police chief constable, said his "thoughts and heartfelt condolences" are with Mr David's family, friends and colleagues.
"After I joined Gwent Police as the chief superintendent for the area covering Caerphilly, I worked closely with Hefin on many occasions and I found him to be an engaging and thoughtful individual.
"A dedicated public servant to Caerphilly, his commitment to our communities will be a significant loss."
Elected to Cardiff Bay in 2016, Mr David was one of the more prominent Labour backbench members and was never afraid to go against the party line.