Pivotal Tuesdays: four elections that shaped the twentieth century

No matter how frustrated or disinterested US voters might be about politics and government, every four years, on the first Tuesday in November, the attention of the nation - and the world - focuses on the candidates, the contest and the issues.

Arguing that the partisan election process has been a way for a messy, jumbled, raucous nation to come together as a slightly more perfect union, Margaret O'Mara looks back at four pivotal presidential elections in the past 100 years, and explores how they shaped the 20th century.