Trump has been president for exactly one year and 79 days. He can serve out the remainder of his term, which would end in 2020, or he could get reelected and sit in office until as late as 2024. To many people, that can and does feel like a long time. But If you think about it, that’s only a slice in the absolute long-term political trajectory. As easy as Trump did away with Obama’s policies, Trump’s successor can do away with his.

Lawyers for Dzhokhar Tsarnaev officially appealed Friday morning to the United States Court of Appeals for the First Circuit, according to Susan Goldberg, the circuit executive for the First Circuit...