President Barack Obama just waged an unprecedented three-week PR campaign to sell Americans and Congress on the need to go to war — six television interviews in one night, a prime-time speech to the nation, and White House outreach to 93 senators and 375 representatives. It’s enough to make those on the left looking for his help on issues such as gun violence, climate change, racial profiling, immigration and jobs wonder whether their causes rate this kind of White House commitment. Is there an intensity gap? “I raised this issue to the president the other day,” Sen. Bernie Sanders, I-Vt.,...