nominee vs favorite son

nominee and favorite son both are nouns.

Word	Noun	Adjective	Verb	Adverb
nominee	Yes	No	No	No
favorite son	Yes	No	No	No

As nouns, favorite son is a hyponym of nominee; that is, favorite son is a word with a more specific, narrower meaning than nominee:

nominee: a politician who is running for public office
favorite son: a United States politician favored mainly in his or her home state

Other hyponyms of nominee include dark horse, running mate, spoiler, stalking-horse, write-in, write-in candidate.

nominee (noun)	favorite son (noun)
a politician who is running for public office	a United States politician favored mainly in his or her home state