Two University of Maryland economists say they have quantified how much Oprah Winfrey's endorsement was worth to Barack Obama: 1 million votes.

The talk show icon has been known to anoint authors to the realm of bestsellers with her support, but Craig Garthwaite and Tim Moore say in a study they released this month that Oprah's influence was strong enough to carry into the Democratic primary.

"Winfrey’s ability to influence the actions of her supporters is impressive. ... Polling evidence suggests that this effect on consumers’ decisions may translate to politics," the economists wrote. "Furthermore, Oprah is regarded as one of the most prominent and influential public figures in the United States: if a celebrity endorsement is ever going to have an empirically identifiable influence, then it is likely to be hers."

Winfrey's endorsement of Obama was her first-ever in a presidential race.

The economists acknowledged in their report that few studies have ever even documented a clear link between endorsements of any kind and voter behavior. But by using geographic statistics for her magazine subscriptions and the sale of books she recommended, they claim to have assessed the voter impact.

Specifically, the economists estimated Winfrey was responsible for 1,015,559 votes in the Obama column, and for increasing voter turnout overall.

Click here to read the full study on Winfrey's impact in the Democratic presidential race.