President Biden’s decision to drop his bid for a second term will be widely attributed to his age and infirmities. We’re skeptical of that. Not that we’re blind. Everyone can see the difficulties he faced. Our reckoning of the failure of Mr. Biden’s effort for reelection, though, is that he had already moved too left for the American voters, on both domestic and foreign affairs. At the end of the fight, he had no way but to come in from the cold.