Final answer:
President Obama's letter to Sasha and Malia is characterized by an expectant tone, reflecting optimism and hope for the future.
Step-by-step explanation:
The overall tone of President Obama's letter to Sasha and Malia is expectant. This tone is evident through his optimistic view on the future and his hope for progress despite the political and social challenges presented during his presidency.
The content provided indicates that President Obama often remained optimistic and charismatic, especially during difficult times such as the economic recovery post-Great Recession, wars, and the implementation of healthcare reform. His rhetoric during the campaign and while addressing issues of race and politics always leaned towards unity and hope, which aligns with the expectant tone conveyed in his letter to his daughters.