As President Donald Trump privately mulled joining Israel’s campaign against Iran this month, one member of his Cabinet sent what he viewed as an audacious attempt to steer him in the opposite direction. At 5:30 a.m. on June 10, Director of National Intelligence Tulsi Gabbard tweeted a cryptic, three-minute video warning that “political elite and warmongers” are “carelessly fomenting fear and tensions between nuclear powers” — and that the world is “on the brink of nuclear annihilation.” Trump saw the unauthorized video and became incensed, complaining to associates at the White House that she had spoken out of turn, according...