Cotton later responded that Ossoff was “trying to wear a black man’s narrative and work like a winter coat.”

The tiff highlights the battle among a field of white candidates to win over a Democratic electorate dominated by black voters. It also underscored the changed dynamic in the race since Ossoff entered in September.

He has captured national attention, quickly emerged as the fundraising leader and is rivaling Tomlinson, a former Columbus mayor who launched her campaign in April, for the biggest share of high-profile endorsements.

And though Tomlinson has not forcefully attacked Ossoff, Cotton has targeted him. She's downplayed his fundraising totals – "if only $ votes," she tweeted – and has dismissed his supporters as people who "don't/can't vote in Georgia."

In a statement, Cotton called Lewis “a national treasure” and accused Ossoff of an “attempt to co-opt his sacrifices for political gain” by referring to Lewis when asked about his own qualifications.

“As a black woman and a black voter, I take umbrage at a candidate melding an endorsement of a civil rights icon into his own bona fides,” she said. “Those are two different things.”

The two contenders are among four top Democrats competing to challenge Perdue, a former Fortune 500 executive with close ties to President Donald Trump. Business executive Sarah Riggs Amico and Clarkston Mayor Ted Terry are also in the race.

Ossoff, a journalism executive who lost a nationally-watched U.S. House bid in 2017, unveiled Lewis' endorsement when he announced his Senate run and weeks later headlined a voter registration rally with the Atlanta Democrat.

At recent events, he’s highlighted Lewis’ support but also the backing of other black elected officials. Ossoff declined to comment, but an aide described the campaign as puzzled that Tomlinson would want to draw even more attention to Lewis’ endorsement.