Democratic demands for Matt Lieberman to ditch his U.S. Senate bid reached new heights Friday as a coalition of left-leaning groups called for him to quit his campaign against Republican incumbent Kelly Loeffler.

The 10 groups joined a public campaign from Democrats across the political spectrum pushing Lieberman to drop out and clear a path for front-runner Raphael Warnock, a first-time candidate backed by party leaders.

“We urge you, with everything we have, to do the right thing for our country, end your race for U.S. Senate, and ensure Democrats stand united behind Raphael Warnock in this unique election,” stated the letter, signed by Democracy for America and other prominent grassroots organizations.

Lieberman, whose father, Joe, is a former Democratic vice presidential nominee, has resisted the mounting calls from party leaders and activists to quit, saying he has as much right to be in the race as Warnock, the pastor of Atlanta’s Ebenezer Baptist Church.

“I don’t begrudge the fans of the team that happens to be ahead right now for wanting to say the game is over, for wanting to pick up your ball and go home. I don’t begrudge anyone for wanting to do that, but it’s obviously ridiculous — entitled and ridiculous,” he wrote in a response sent to The Atlanta Journal-Constitution.

“With respect for your tens of thousands of Georgia members, I will defer to the judgment of the millions of Georgians who have a right to vote in this election," he added. "I am comfortable living with their decision whatever it may be.”

The pressure has intensified as some polls, including an AJC survey, showed Warnock neck-and-neck with Loeffler and Republican U.S. Rep. Doug Collins in the crowded special election.

Since no candidate is likely to win more than 50% of the vote in November, a January showdown between the two top finishers in the 21-candidate race is expected. Some Democrats worry that Lieberman’s presence in the race will siphon enough votes from Warnock to lock him out of the runoff.

Still, there are other signs Warnock need not worry. A Quinnipiac University poll released this week showed Warnock with a sizable lead over the two Republicans, and Lieberman in the single digits. And Warnock’s vast fundraising edge — he will report raising nearly $13 million over the past three months — has financed an ad barrage that’s raising his profile.

The Rev. Raphael Warnock, the pastor at Atlanta's Ebenezer Baptist Church, is the front-runner among Democrats running in November's special election for the U.S. Senate. A Quinnipiac University poll released this week showed that Warnock also holds a sizable lead against the two leading Republicans in the contest, U.S. Sen. Kelly Loeffler and U.S. Rep. Doug Collins. (Hyosub Shin / Hyosub.Shin@ajc.com)

Credit: HYOSUB SHIN / AJC

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Credit: HYOSUB SHIN / AJC

Even if Lieberman abandons the race, it’s too close to the November special election to take his name off the ballot. Another long-shot candidate, A. Wayne Johnson, will also still be an option for voters even though he ended his campaign Thursday.

Still, state and national Democratic leaders don’t want to leave much to chance.

Over the past week, two former presidents — Jimmy Carter and Barack Obama — endorsed Warnock. And on Friday, two Democratic senators spanning the party’s ideological divide vouched for him: Bernie Sanders of Vermont, a democratic socialist, and Alabama’s Doug Jones, a centrist.

It’s the opposite of the dynamic on the Republican side of the contest. At a campaign stop last week in Atlanta, President Donald Trump urged both Collins and Loeffler to stay in the contest to spur additional Republican turnout.

The groups that penned Friday’s dispatch to Lieberman acknowledged that they would normally “be some of the very last groups to encourage any Democrat to drop out of a primary.”

“However, every rule has exceptions,” the letter stated, “and this is one of those.”