Today’s Democrats may be unusually conflict averse for a modern liberal party, but even stalwart leaders succumb to it. Abraham Lincoln was our greatest president, but he replaced his staunchly anti-slavery vice president with a southern bigot as a gesture of good will to the authoritarian-minded hoi polloi of the era. It set the country on a course to win the Civil War but lose the civil peace. More than a century and a half later, his heirs in the modern Democratic Party seem poised to repeat his greatest error