South Carolina
Gubernatorial
Greenville County (once home to some of my family) is in all likelihood the county that South Carolina Democrats need to flip to win the state (at least federally in application of uniform shift). In 2018, however, now-Governor McMaster won the county by an even 16 points, doing significantly better than his statewide margin. As Greenville, Simpsonville, and other suburbs continue to shift to the left, this reality will draw even closer
Berekley County is part of the red wall of counties surrounding Charleston. While Smith posted a very good showing for a Democrat in South Carolina, he still fell 7 points short in Berekley, which he likely needed to flip to win. Republican strength is concentrated around Monck's Corner and the suburban strip bording Charleston
Horry County is home to Myrtle Beach and Coastal Carolina University, and is among the largest red counties in the state. In 2018, even with comparatively poor margins statewide, McMaster won the county by 30 points. Areas where he found the least support were typically majority African American, with some more educated whites in Conway also voting more against him than in other areas
Presidential
Dillon County SC sits in the northeast of the state, across the border from North Carolina's politically complex Sandhills. After voting Democratic for a long time, Trump won it in 2020 by just over a point. African Americans still broke heavily Democratic, but rural whites becoming more Republican and out-migration of African Americans helped swing it to Trump