Oprah Winfrey told CNN today that she is “100% behind Barack Obama” — and said that she “would do whatever I thought would be of service” during the campaign.

Winfrey’s endorsement in 2008 helped in campaign organizing and fundraising, as she went on the trail with him in Iowa, New Hampshire and South Carolina and held a donor event at her home in Montecito, Calif.

She didn’t give any indication of what she would do this time around, but told CNN, “If he or his office called me tomorrow and said that they needed me I would do whatever I thought would be of service. I did what I did in 2008 because I really thought that would be of value and of service. I don’t think that’s needed in 2012. There’s not a person in the world who doesn’t know who Barack Obama is.”

She also called Obama a “masterful leader,” and predicted that he would be reelected.

Two researchers at the University of Maryland concluded that Winfrey’s endorsement of Obama netted more than 1 million votes.