The word on everyone’s lips in Washington now — in newsrooms and advocacy groups, in congressional offices and embassies — is “firehose.” As in the high-pressure stream of White House orders. The daily deluge of Donald Trump’s tweets blaming “so-called” judges for future terror attacks and assailing Nordstrom for dropping his daughter’s clothing line for poor sales. The tsunami of statements inflating the murder rate and hyping the terrorist threat, while aides mind-bendingly blame the media for not covering massacres in Bowling Green and Atlanta that never happened. With each new volley, drinking from the Trump firehose feels ever more...