One of the young wordsmiths behind President Obama’s oratory is leaving the administration, a crack in a close-knit speechwriting team that helped propel Obama to the White House and has played a major role in shaping his words ever since. Adam Frankel is leaving to become executive director of Digital Promise, a new nonprofit group that will explore ways technology can be used to strengthen education. “I worked with the president on a lot of his education speeches,’’ Frankel said in an interview Friday. “So I was thinking about what I want to do and I realized that I wanted...