white hope 
noun
A person expected to bring much success to a team or organization: the great white hope of the Tory Left...
- Suede were the great white hope of indie rock for a while; everyone was expecting them to fill in the gap left by the Smiths.
- Maybe some of our stars aren't running so well at the moment so he is now the great white hope!
- Having been rejected by the Tories, the man formerly regarded as the great white hope of the British right has refused all interviews and even turned down a request from the student newspaper.
Origin
1911: originally referring to a white boxer thought capable of beating Jack Johnson, the first black world heavyweight champion.