Perhaps Winfrey's most consequential endorsement would be the one she made during the Democratic primaries in 2007, when she backed first-term senator Barack Obama against the presumptive nominee, Hillary Clinton. Campaigning with Obama in Iowa, New Hampshire, and other important states, Winfrey may have been responsible, according to one analysis, for between 420,000 and 1.6 million votes. If so, it is possible that Winfrey's support won Obama the nomination, and consequently, the presidency.

Tim Wu, The Attention Merchants, loc. 809