Belz...
Fiend God
Very well, let's agree that the word "unelectable" means "didn't win an election". Which means a) it can only be applied in hindsight and b) an unelectable person can go on to win a later election. Like Nixon who was unelectable after he lost in 1960 but he became electable after he won in 1968.
If that's what it means, we already have a phrase for that: "they lost."