Former President Barack Obama will join Georgia Democratic Senate candidates Jon Ossoff and Raphael Warnock for a virtual rally Friday as the two U.S. Senate runoffs are little more than one month away and the control of the upper chamber hangs in the balance. 

Obama earlier this week appeared in an ad for Ossoff, but Friday will mark the first time he joins a Georgia Senate campaign event live. The virtual rally comes on the same day Vice President Mike Pence is set to campaign in Georgia for incumbent Sens. Kelly Loeffler and David Perdue. It will be Pence's second trip to the state in recent weeks. President Trump, meanwhile, will campaign in Georgia for the Republicans on Saturday. 

That leaves President-elect Joe Biden as the only president or vice president from the past two administrations not to actively campaign with his party's Senate candidates in Georgia. That could change soon, however. Incoming Biden chief of staff Ron Klain said on ABC's "This Week" that he expects Biden to campaign in Georgia for Ossoff and Warnock.

Former U.S. President Barack Obama speaks at the opening of the Bits & Pretzels meetup on September 29, 2019 in Munich, Germany. Obama will campaign in Georgia for Raphael Warnock and Jon Ossoff on Friday. (Photo by Hannes Magerstaedt/Getty Images)

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Stacey Abrams, a top Democratic figure in Georgia, will also join the virtual rally Friday. 

"With early voting starting Dec. 14, Friday's event with President Obama, Rev. Warnock, and Stacey Abrams will inspire this historic statewide movement to generate record-shattering turnout so we can end this COVID crisis, deliver affordable health care for all Georgians, and pass a new Civil Rights Act," Ossoff said in a statement. 

Added Warnock: "President Obama knows what we do: Georgia voters will decide the future of our nation, from passing COVID relief to protecting our voting rights. With his help, we will win this election for Jon Ossoff and Raphael Warnock and take back the Senate for working families across this country."

The involvement by Obama, Biden, Pence and Trump – plus statements, endorsements and rally appearances by many others in the Georgia races – underscores the value both parties place on control of the U.S. Senate in the next Congress. Democrats will control the House of Representatives, meaning that if they are able to gain control of the Senate as well, they will have two years largely unencumbered to enact the Biden agenda. 

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Democrats would need to win both of the Georgia races to do that, thereby bringing the Senate to an effective 50-50 deadlock and leaving Vice President-elect Kamala Harris to break ties on party-line votes. If Republicans win even one of the Georgia Senate seats, however, they will have a majority, allowing them a significant say in much of Biden's agenda, from health care legislation to Cabinet appointments to judges. 

"Will be going to Georgia for a big Trump Rally in support of our two great Republican Senators, David and Kelly," Trump said in a tweet Wednesday. "They are fantastic people who love their Country and love their State. We must work hard and be sure they win."

Responded Perdue: "Excited to welcome @realDonaldTrump back to Georgia! Everything is on the line in this election, and I appreciate the President’s full support of @KLoeffler and me as we fight to save the Senate!"

"I’m SO proud to have our President’s support & thrilled to welcome him back to Georgia!" Loeffler said. 

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The president's son, Donald Trump Jr., who is rumored to have political aspirations of his own, also got in on the act this week. He is starring in new ads being run in Georgia by a PAC run by two of his top aides. 

With the high stakes in Georgia, the runoffs are set to be some of the most expensive two months of non-presidential politics in American history. 

As of Monday, the campaigns, political parties and outside groups like PACs had already spent more than $280 million on TV ads, according to AdImpact, a top national ad tracking firm formerly known as Advertising Analytics. That spending is on pace to potentially break half a billion dollars before voters head to the polls. 

Fox News' Paul Steinhauser contributed to this report.