Of course it has nothing to do with the fact that when she did it in 2008 the wheels fell of the bus and her ratings tanked, never to return to their former glory.

Via RCP:

Oprah Winfrey tells CNN she still supports President Obama, however she will not do a large endorsement event like she did during the 2008 campaign cycle.

“No, I don’t think it’s necessary because my endorsement is that I am a 100% supporter of him. And if he or his office called me tomorrow and said that they needed me I would do whatever I thought would be of service,” she said.