Former President Barack Obama on Friday endorsed Raphael Warnock’s U.S. Senate campaign, becoming the latest Democrat to rally behind the pastor’s challenge to U.S. Sen. Kelly Loeffler as pressure mounts on his rivals to drop out of the free-for-all race.

Obama also backed Jon Ossoff’s challenge to U.S. Sen. David Perdue and nine down-ticket Georgia candidates in competitive elections, including U.S. House candidates Lucy McBath and Carolyn Bourdeaux and state House Minority Leader Bob Trammell.

The development comes as Warnock aims to consolidate Democrats behind his campaign - and his allies urge Matt Lieberman, another Democrat in the contest, to abandon his bid.

Lieberman, a former educator and entrepreneur, has flatly rejected talk of quitting and insists he has the same chance as Warnock in the November special election, which features 21 candidates who qualified for the race and no party primary to filter out nominees.

On Friday, Lieberman said Obama has endorsed “every DC-sponsored” Senate candidate. “No, you won’t be beholden to the bosses at all....," he said of Warnock on Twitter.

A series of polls released this week by the AJC and other outlets suggest Lieberman’s chances of seriously contesting the seat are dim. The polls show Warnock bunched up with Loeffler and U.S. Rep. Doug Collins with around 20% of the vote. Lieberman hovers around 10% and Ed Tarver, another Democrat, lags further behind.

Associate minister Selina Smith, Rev. Raphael Warnock, Sen. Barack Obama and associate minister Shanan Jones hold hands and sing "We Shall Overcome" along with the rest of the people gathered at Ebenezer Baptist Church Sunday.

Credit: Jessica McGowan / AJC

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Credit: Jessica McGowan / AJC

Democrats are fretting because they fear that Lieberman’s presence in the contest will siphon just enough votes away from Warnock to allow the two Republicans to squeeze ahead, depriving the party of a shot in a January runoff between the top finishers.

Obama and Warnock have a long history, including a 2008 visit to the pastor’s famed Ebenezer Baptist Church where the two locked arms in prayer. More recently, Obama and Warnock shared the pulpit in July for the funeral of civil rights hero John Lewis, when the former president used his eulogy to press for an expansion of voting rights.

In a statement, Warnock said he would fight to preserve Obama’s policies if elected.

“With the Affordable Care Act under siege and our constitutional right to vote being threatened," he said, “Georgians and all Americans deserve leaders in Washington who are committed to doing the people’s business.”

Obama’s Georgia endorsements:

Jon Ossoff, U.S. Senate

Rev. Raphael Warnock, U.S. Senate

Lucy McBath, U.S. House, District 6

Carolyn Bourdeaux, U.S. House, District 7

Sara Tindall Ghazal, State House, District 45

Nakita Hemingway, State House, District 104

Regina Lewis-Ward, State House, District 109

Mokah Johnson, State House, District 117

Robert Trammell, State House, District 132

Joyce Barlow, State House, District 151

Matielyn Jones, State Senate, District 45