MARIETTA, Ga. — There were dozens of Jon Ossoff signs at the rally outside the Cobb County Civic Center, but the touring campaign bus, the bulk of the applause and the final words belonged to the Rev. Raphael Warnock, who used them to boost two Democratic Senate campaigns.

“Georgia is positioned to do a marvelous thing,” Warnock told the crowd. “Send a young Jewish man, the son of immigrants, who sat at the feet of Congressman John Lewis, and a kid who grew up in the public-housing projects of Savannah, Georgia, the pastor of Martin Luther King Jr.’s Ebenezer Baptist Church, to the United States Senate at the same time.”

Two weeks into the extraordinary runoff races that will decide which party controls the U.S. Senate, Warnock and Ossoff have combined their efforts to try to win Georgia’s pair of Senate seats. Their names are stacked together on yard signs; they’ve called each other “brother” at joint campaign appearances. But it is Warnock who is animating the Democratic base — and the Republican opposition.

That’s because both sides are treating Warnock, the fiery 51-year-old preacher who leads the legendary Atlanta church associated with King, as the key factor in determining who wins the Jan. 5 races. Democrats hope his presence on the ballot can sustain the energy of Black voters who helped hand Georgia’s electoral votes to a Democratic presidential candidate for the first time since 1992. Republicans, likewise, see Warnock as a threat as well as a ripe target, unleashing a torrent of attacks designed to tarnish his appeal and mobilize GOP voters despite finger-pointing in the party over President Trump’s defeat in the state.

“He is the charismatic pastor of the most important Black church in Georgia — a church of enormous historical importance,” said former House speaker Newt Gingrich, who represented an Atlanta-area district from 1979 to 1999, explaining the potency of Warnock’s appeal. “And he understands how to communicate to a very large group of people.”

Republican attacks have focused on Warnock’s support of Barack Obama’s controversial former pastor, the Rev. Jeremiah Wright, and an old sermon in which Warnock declared, “You cannot serve God and the military.” Democrats have highlighted his origin story in the Kayton Homes projects in Savannah and his fight for health care while leading a church at the symbolic center of the civil rights movement.

Warnock “carries with him the hopes and aspirations of people who see someone who grew up with a life similar to theirs,” said former Georgia gubernatorial candidate Stacey Abrams, a Democratic star whose voter registration efforts are widely credited with helping to flip the state. “He grew up in a housing project in Savannah. He is someone who speaks authentically to their worries and their concerns. … And so I do think that the fire being trained against him is a signal of how strong of a candidate he is.”

The runoffs pit challenger Ossoff (D), a 33-year-old documentary filmmaker, against Sen. David Perdue (R) and Warnock against Sen. Kelly Loeffler (R). The runoffs were triggered when none of the candidates got more than 50 percent of the vote in the Nov. 3 election.

Democrats will still hold the majority in the U.S. House, but Republicans have a 50-to-48 advantage in the Senate. If Warnock and Ossoff both win, they would knot the upper house at 50 seats for each party, with the tie-breaking vote belonging to Democratic Vice President Kamala D. Harris once she takes office on Jan. 20. The success of the Ossoff-Warnock pairing will determine whether Joe Biden’s administration is able to enact an ambitious agenda or whether Republicans can blunt Democratic power.

The contours of the race could still shift in the coming weeks. Both sides are waiting to see how much of a role President Trump will play in Georgia. He continues to dispute the outcome of the general election, spreading false narratives about widespread voter fraud, including in Georgia, which completed a recount that confirmed Biden’s victory. Perdue has privately worried that Trump’s power might be waning and that continued support of the president could have political costs. Publicly, he and Loeffler have followed Trump’s lead and questioned the integrity of the vote — and called for the resignation of Republican Secretary of State Brad Raffensperger, saying he mismanaged the election.

Trump has tweeted support for the Republican candidates but has not announced whether he will come to Georgia to campaign.

For now, much of the attention is on Warnock — especially from Republicans.

Loeffler highlighted GOP concerns about Warnock, and pointed to what the party sees as his political vulnerabilities, in a call with donors this month. She complained that he had “escaped unscathed” from a general-election race that also featured a bitter fight between her and fellow Republican Douglas A. Collins. Details of the call were shared with The Washington Post by a person who provided a precise account of the discussion.

In the same call, Perdue was dismissive of Ossoff, whom he called “a 33-year-old who has never done anything."

Loeffler outlined the Republican playbook against Warnock, calling him “the most radical Democrat on the ballot this year” and listing several associations that have been featured in a stream of GOP attack ads.

“He welcomed Fidel Castro to his church in the ’90s,” she said. “He called the Rev. Jeremiah Wright a prophet.”

In mentioning Wright, Loeffler was referring to Warnock’s 2008 defense of Obama’s former pastor, who was accused of being anti-Semitic and preaching an incendiary sermon that included the phrase “God damn America.”

In 2009, Wright claimed “them Jews” were stopping Obama from talking to him. He later apologized, saying he misspoke and was referring to Zionists, not all Jews.

Warnock has said that the 1995 invitation to Castro that Republicans have highlighted happened at a church where he was a youth pastor and that he had no say in the decision. Loeffler has also attacked Warnock over a 2002 arrest on obstruction charges by authorities investigating an abuse case at a summer camp run by his church. The charges were dropped, and police said Warnock was cooperative. He has said that the charge resulted from an overzealous investigator and that he had insisted only that teenage camp counselors have access to a lawyer.

Still, the strategy to link Warnock to controversy was apparent last week, when Vice President Pence told a crowd in Canton that the pastor had “demeaned our military and repeatedly defended the anti-Semitic rhetoric of Reverend Jeremiah Wright."

Brendan Buck, a longtime former Capitol Hill aide from Georgia who is now a Republican operative, said Ossoff is viewed as less of a threat because Republicans have had success against him. Ossoff lost a House special election in 2017. And although the Nov. 3 election was close enough to merit a runoff, Ossoff trailed Perdue by more than 80,000 votes.

Warnock is “going to be the one they’re focusing on because he’s said more stuff that’s out there for them to latch onto,” Buck said. “He’ll be the stronger candidate, but he’ll also be the bigger target in this pact they’ve formed.”

On the campaign trail, Warnock has touted his humble roots growing up in the Kayton Homes housing projects and has said Georgia’s politicians need to do a better job of reflecting the state’s most vulnerable citizens.

“I won’t forget about the coast,” he said in Midway on Sunday. “I’m not going to forget about my own mother. I will remember you. Because I’m from this part of the state."

He was the 11th of 12 children. His parents were both preachers, though his father also hauled old cars to a local scrap yard for money. As a boy, he listened to the radio show of Otis Johnson, who spoke of Black empowerment on a Savannah-area station. From a young age there was little doubt that the teen nicknamed “Rev” in high school would follow in his parents’ footsteps.

He idolized King, sometimes mimicking the cadence and timbre of the civil rights leader’s voice, said people who knew Warnock as a child. Like King, he attended Morehouse College, a historically Black school in Atlanta. In 2005, at age 35, Warnock became the youngest senior pastor at Ebenezer Baptist Church, the spiritual home of King, which has for decades been at the symbolic center of activism in Atlanta.

Under Warnock, the church has continued to exist at the intersection of piety and racial justice. Lewis’s funeral was held there in July. And from the same pulpit, Warnock eulogized Rayshard Brooks — a Black man shot by police who encountered him sleeping in the drive-through lane of an Atlanta Wendy’s. Atlanta’s police chief resigned the next day as protests engulfed the city.

Warnock “consoled a family that was crying and kids who have seen their father murdered on video, and it was about church,” said L. Chris Stewart, who represented Brooks’s family and credits the church service with helping to calm tensions in the city after the killing. Warnock “could have made that service a massive spectacle — open to the whole world, open to the public. He could have made it a huge circus, media affair, but he literally was not allowing it. It wasn’t going to happen. He wanted it to be a service and not press conference.”

Warnock was also arrested on the steps of the Georgia Capitol in 2014, protesting the then-governor’s decision to not expand Medicaid under the Affordable Care Act.

The Rev. William Barber, the co-chair of the Poor People’s Campaign, said Warnock has long focused on issues such as health care that affect poor people of all races, which has particular resonance in a state hit hard by the coronavirus crisis.

“The pain of covid is forcing a lot of people to reassess who they’ve been voting for, and once they voted for what [elected leaders] ended up doing,” Barber said.

“He’s speaking to people in the center of their pain and the center of their misery and the middle of their hurt,” Barber said. “So actually the fact that they’re throwing so much at him shows his power. The power to bridge the gap of race, and the power to not just be a Black candidate but a moral candidate, a candidate that speaks to what’s going on in the center of people’s lives in Georgia.”

On Thursday, Alvin Farmer, of Clayton County, showed up to an outdoor, socially distanced rally for Warnock and Ossoff wearing a shirt that said “Black Lives Matter” on the front and had pictures of victims of police violence on the back.

He said he planned to vote for both Democrats, moved by the thought of sweeping reforms throughout the nation, but he conceded he was much more familiar with Warnock than Ossoff. Farmer is not a member of Warnock’s church but was moved by the pastor’s words at Lewis’s funeral.

But he said he only recently learned enough about Ossoff to merit his consideration.

“I didn’t vote for him because I don’t just vote for somebody I don’t know,” said Farmer, who is Black and says he is an independent. After the general election, “I saw a commercial where he had worked for John Lewis. I think he should have played that up more.”

Tom Hamburger and Robert Costa contributed from Washington to this report.

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