CNN Washington Bureau

DES MOINES, Iowa (CNN) -- Saying she felt compelled to support "the man I believe has a new vision for America," Oprah Winfrey spoke passionately about Democratic presidential hopeful Barack Obama at a rally in Iowa Saturday.

"These are dangerous times, you can feel it. We need a leader who shows us how to hope again in America as a force for peace," Winfrey told the enthusiastic crowd.

"I believe Barack Obama will bring statesmanship to the White House," she said. "He's a man who knows who we are and knows who we can be."

Winfrey said she has voted for as many Republicans as she has Democrats over the years, so her endorsement wasn't about partisanship.

"This is very, very personal. I'm here because of my personal conviction about Barack Obama and what I know he can do for America," she said to applause.

Obama thanked Winfrey for drawing a big crowd and coming out to the event.

"There are some people here who are here to see Oprah. I'm sort of a by-product of that and I appreciate that, but what I know is that for her to take the risk of stepping out of her comfort zone is extraordinary," the senator from Illinois said.