Answer: Primary election turnout might have something to do with it?
Nathaniel, I can imagine a few factors played into how the Georgia state Supreme Court race is playing out. For one thing, state Supreme Court races are usually sleep affairs in Georgia, and control of the court wasn't up for grabs. But it's pretty clear that turnout was pretty low across the state, even for a primary. In the 2022 midterms, about 1.9 million people cast votes in the Democratic and Republican primaries for U.S. Senate; so far tonight, around 667,000 votes have been counted, which per the AP is 56 percent of the expected vote. So there might be about two-thirds as many voters in this race than in the 2022 primaries in Georgia.
It also looks like turnout in the Atlanta area was especially low, with great consequences for the liberal/Democratic candidate. For instance, about half the vote is in from Fulton County, one of the bluest in the state, and Barrow only leads there by 6 points compared with Biden's 46-point edge there in 2020.
—Geoffrey Skelley, 538