When you cast a vote for the winning presidential candidate, it’s easy to understand why you might be optimistic about the future. So why do some presidents deliver on those high hopes when others don’t? This hour, we’ll talk about the idea with Elaine C. Kamarck, senior Brookings fellow and founding director of the Center for Effective Public Management. Her new book is called “Why Presidents Fail: And How They Can Succeed” (Brookings).