Kamala Harris’s book 107 Days confirms two truths: Joe Biden never should have sought re-election and she did not belong on a national ticket. Biden was snared by Father Time and hubris. The 46th president was not the transformational figure he saw in the mirror. More than half the US rated him a failure. “People hate Joe Biden,” Harris quotes David Plouffe, her senior strategist and an Obama White House veteran, as saying. What’s unstated is that Harris was never a vote-magnet. When she ran for attorney general of California in 2010, she won by less than 1%, a margin...