For more than a century and a half, the American postal system has served as a quiet guarantor of democratic participation — carrying ballots from Civil War encampments to modern kitchen tables. On Monday, the Supreme Court drew a firm line around that tradition, rejecting President Trump's effort to expand the Postal Service's authority over election administration. The Court found that such a move exceeded executive power, affirming that the architecture of voting — even where it touches the mail — belongs to Congress and the states, not to the White House alone.