Douglas Harper's Etymology Dictionary
white hope
1911, originally in U.S. sporting use in reference to the quest for a white man capable of beating champion pugilist Jack Johnson.
WordNet
white hope
n. someone (or something) expected to achieve great success in a given field; "this company is the great white hope of the nuclear industry's waste management policy" [syn: great white hope]
Usage examples of "white hope".
Holmes had the delicate job of convincing our precinct workers that Frances was our new white hope.
I thought you were supposed to be our white hope with the military.