Winfrey, who took the stage to booming applause, said she wanted to come to Georgia to support Abrams because she saw how Abrams is "handling herself" amid an onslaught of "haters".
"I am here today because Stacey Abrams cares about the things that matter", she said to a mostly female audience north of downtown Atlanta.
The actress is set to hit the campaign trail for Abrams this week and gave a heartfelt speech at Thursday's event.
"We have this incredible opportunity to make history", Winfrey told the capacity crowd "We have our inalienable right to vote because the one place where we are all equal, is at the polls".
"I'm here today because of the men and because of the women who were lynched, who were humiliated, who were discriminated against, who were suppressed, who were repressed and oppressed, for the right for the equality at the polls", Winfrey said. "Oprah Winfrey has a spiritual connection with so much of this country, and it was built over years and years of doing that talk show", McDowell said on Fox News's "Outnumbered". "You are disrespecting and disregarding their legacy, their suffering and their dreams, when you don't vote".
Federer beats Medvedev to reach 14th final at Swiss Indoors
World No 11 Nishikori's luckless run means that a win in Memphis in 2016, his second career title, remains his most recent. Federer won his 20th straight match at the tournament and has played in 12 straight Basel finals.
Some 120 kilometres north, Vice-President Mike Pence stood alongside Abrams' opponent, Brian Kemp, in Dalton, and mocked the billionaire media icon as just another liberal outsider trying to impose on Republican-run Georgia.
"Democracy is not just about our individual rights and concerns and our individual protections", Winfrey said, "but rather it lives and thrives in making sure that everybody is lifted by the community".
Abrams is running on a campaign that includes Medicaid expansion, and "common-sense gun control", Winfrey noted.
More than 1.5 million of the state's nearly seven million registered voters have cast ballots already. I don't want to run.
"I got a message for all of Stacy Abram's liberal Hollywood friends", he continued.