running mate vs candidate

running mate and candidate both are nouns.

Word	Noun	Adjective	Verb	Adverb
running mate	Yes	No	No	No
candidate	Yes	No	No	No

As nouns, candidate is a hypernym of running mate; that is, candidate is a word with a broader meaning than running mate:

running mate: a nominee for the lesser of two closely related political offices
candidate: a politician who is running for public office

Other hypernyms of running mate include campaigner, nominee.

running mate (noun)	candidate (noun)
a nominee for the lesser of two closely related political offices	someone who is considered for something (for an office or prize or honor etc.)
	a politician who is running for public office