Donald Trump stood on stage in Atlanta on Thursday night and told an insane lie: Democrats, he said, want to “kill the baby.”

“They will take the life of a child in the eighth month, the ninth month, and even after birth — after birth — if you look at the former governor of Virginia, he was willing to do this. He said, ‘We’ll put the baby aside, and will determine what we do with the baby,’ meaning: We’ll kill the baby.”

This was an easy one, practically teed-up for...