Abby Phillip John Wagner Anne Gearan The Washington Post

Just days before the election, after weeks believing that Michigan was safely blue, the pro-Hillary Clinton super PAC Priorities USA polled voters there - only to discover that it was a one-point race.

Sen. Bernie Sanders pulled off a narrow upset in the Michigan primary Tuesday, buoying his challenge to Democratic front-runner Hillary Clinton and giving him bragging rights to a big, diverse state outside his previous areas of strength.

Just days before the election, after weeks believing that Michigan was safely blue, the pro-Hillary Clinton super PAC Priorities USA polled voters there - only to discover that it was a one-point race.

Sen. Bernie Sanders pulled off a narrow upset in the Michigan primary Tuesday, buoying his challenge to Democratic front-runner Hillary Clinton and giving him bragging rights to a big, diverse state outside his previous areas of strength.