Election officials and researchers from Arizona to Taiwan are adopting a radical playbook to stop falsehoods about voting before they spread online, amid fears that traditional strategies to battle misinformation are insufficient in a perilous year for democracies around the world.Modeled after vaccines, these campaigns — dubbed “prebunking” — expose people to weakened doses of misinformation paired with explanations and are aimed at helping the public develop “mental antibodies” to recognize an...