white hope
The person or thing expected to bring great success or fortune to someone or something. Since being signed last spring, many are talking about the rising football star as the team's white hope. While a great politician, I think it's wrong to see her as some white hope of the party.
white hope
a person expected to bring much success to a team or organization. The expression originated in the US in the 1910s as an epithet applied to a white heavyweight boxer who it was hoped (by whites) might beat Jack Johnson, the first black boxer to hold the world heavyweight title ( 1908–15 ).
1941 Lord Berners Far from the Madding War He was a composer: the white hope (so a critic had described him) of English music.