Kemp - who, as Georgia secretary of state, is also in charge of elections and voter registration - faced backlash after it was reported his office had put more than 53,000 voter applications on hold, almost 70% of which are from African-Americans, because they failed to clear the state's controversial "exact match" standard.
Kemp is a staunch conservative who has embraced U.S. President Donald Trump and the administration's hard-line on immigration.
Abrams would be the nation's first black female governor.
She agreed with the panel that Winfrey exists in her own class of star power, though McCain concluded by saying Abrams' victory is not assured just because Winfrey stands beside her. During his speech, Pence tried to counter Abrams' liberal appeal with a folky message: "This ain't Hollywood". Vice President Mike Pence had the ideal response by channeling Will Ferrell in "Anchorman".
"Go with God, go with goal, go with your values, upholding everything we believe to be true about Stacey Abrams and why we're all voting for her", Winfrey said.
With the midterm elections less than a week away, Americans are gearing up for one of the most important elections of our lifetimes.
Speaking on CNN's "State of the Union "on Sunday, Abrams called the announcement a distraction and political move to sway voters in the final hours of the race".
"This ain't Hollywood!" said Pence Thursday at a rally in Savannah. They don't help. Just ask Hillary Clinton.
As a black woman, Winfrey noted her kinship to two groups historically denied ballot access in the United States.
"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".
Kemp is now facing off with Democrat Stacey Abrams for the governorship in a tight race.
Videos uploaded to Ms Winfrey's and Ms Abrams' social media showed the television personality knocking on doors canvassing for the hopeful governor.
Abigail Collazo, Abrams' director of strategic communications, condemned the robocall and said both Trump and Kemp have contributed to a poisonous atmosphere, adding that Kemp has responded with silence on previous racial attacks on Abrams.
On Saturday, it was reported that racist robocalls bankrolled by white supremacists were targeting Abrams and Winfrey.
Winfrey and Abrams greet a crowd gathered for a town hall conversation in Marietta, Ga.