If patterns from 2008 are any indication, the media mogul's absence from the stump could make the president's reelection a little bit harder.

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Oprah Winfrey campaigns with Barack and Michelle Obama in Des Moines in December 2007. Reuters

Back in the heady days of May 2007, when Oprah Winfrey endorsed Barack Obama, the future looked bright for both of them. Five years later, they've both gotten somewhat bogged down. Obama, of course, won the presidency, but inherited a nation in the throes of recession. While the economy is back on course, he still faces a tough road in his quest for reeelection.

And he'll be down one major asset: Oprah herself. That's because Winfrey's gotten sidelined too. In 2009, she announced she was leaving her outrageously popular daytime TV show to create her own cable network, but the Oprah Winfrey Network has proven to be a harder proposition than she expected. Turnover has been high, ratings have been low, and Oprah says she can't take time off to stump for the president this year.

"I actually love our president and have the utmost respect for him and that office and what it takes to be there," Winfrey said on CBS's Early Show, adding that she still backs him "100 percent." "I will not be out because I'm trying to fix a network."

So could this hurt Obama in the general election? Laugh all you want, but it's a serious question. (The Wikipedia entry for "Oprah Winfrey's endorsement of Barack Obama" is disturbingly comprehensive.) In fact, political scientists Craig Garthwaite and Tim Moore set out to determine what effect her endorsement had on Obama in the 2008 Democratic primary. And guess what? It was pretty large (emphasis added):

Our results suggest that Oprah Winfrey's endorsement of Barack Obama prior to the 2008 Democratic Presidential Primary generated a statistically and qualitatively significant increase in the number of votes Obama received as well as in the total number of votes cast .... In total, we estimate that the endorsement was responsible for 1,015,559 votes for Obama. The 95 percent confidence interval around this estimate is higher than the difference in votes between Obama and Hillary Clinton in our sample. This suggests that Winfrey's endorsement was responsible for the difference in the popular vote in our sample.

That's right: Per their research, Oprah's endorsement accounted for about 5 percent of Obama's primary votes. They calculated this by correlating primary votes with circulation of O: The Oprah Magazine and sales of books she recommended, then controlled for a variety of factors.

There are good reasons to believe it won't matter as much this year. For example, the research covered the primary, not the general election. And for another, Oprah's endorsement was hugely helpful in creating publicity for Obama, then an underdog to Hillary Clinton, but for an incumbent president, name recognition isn't nearly as important. Third, her influence may have diminished since her departure from network TV. But that doesn't mean that it wouldn't be helpful for her to be out on the stump in the coming months. Even if voters back Obama, her influence in driving turnout could be useful in a year when Democrats' enthusiasm has lagged well behind Republicans'.

Maybe there's a silver lining, though: A thriving OWN could be part of the economic resilience Obama will need for reelection.

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