Barack Obama, an old-fashioned ward boss, orchestrates the president’s removal. Democracy took a devastating hit on Sunday when President Biden withdrew from the presidential race. Along the way, he got it wrong. It isn’t Donald Trump who is an existential threat to our democracy. It’s Barack Obama. In the old-school way of Chicago backroom politics, Mr. Obama was the conductor of the band that successfully orchestrated the removal of the presidential candidate chosen by more than 14 million Democratic primary voters—to be replaced by someone he and the party bosses choose instead. It’s classic ward-boss tactics. I’ve known Mr. Obama...