“The Great Mentioner” describes the phenomenon whereby certain people are “mentioned” to journalists as possible candidates for higher office.
As Scott Simon of National Public Radio explained:
The late Art Buchwald used to talk about the Great Mentioner — some unnamed person who told pundits and reporters a lot of people say this, a lot of people say that. Art said that if you trace back exactly who said this and that, it was usually just the reporters and analysts themselves that tried to splash a coat of credibility over sheer speculation by putting it in the mouth of the Great Mentioner.
Ryan Lizza attributes the term to New York Times columnist Russell Baker who used it “to describe the mysterious source who plucks politicians from obscurity and mentions them to political journalists as contenders for higher office.”