I've only ever heard the word "dauphin" in the context of a French crown prince (starting with Charles V, when Philip VI gave him the Dauphiné region to rule while he was still the heir). Is the term used more universally?
‘I have been asked whether I wish to nominate a successor, an inheritor, a dauphin or delfino. I have decided to name Christopher Hitchens.'
I’ve seen other examples in this style. Maybe folks in comments can point out more.