They called it the "Big Send." Democrats gathered in living rooms, libraries, and coffee shops across the country to write letters to millions of potential voters in swing states and competitive congressional districts, urging them to vote in November. During the 2020 pandemic election, the novel but decidedly 20th-century tactic had cut through the glut of digital messages that inundated Americans’ cellphones and inboxes, and organizers hoped it would similarly boost turnout for Democrats in 2024.