It is the rare occasion when Obama lets his Spock mask slip. But November 2, 2016, was just such a moment. Six days before the presidential election, when addressing the Congressional Black Caucus, he stressed that the Republican candidate, Donald Trump, threatened hard-won achievements of blacks: tolerance, justice, good schools, ending mass incarceration ?" even democracy itself. "There is one candidate who will advance those things," he said, his voice swelling with emotion. "And there's another candidate whose defining principle, the central theme of his candidacy, is opposition to all that we've done."