The Dems in NoVA use early/absentee voting to pile up huge numbers prior to election day. They have a formidable GOTV machine. I worked as both a poll watcher and election officer in Fairfax County for over 30 years along with being active in local Rep politics. The Dems won Fairfax County in 2004 in the Presidential race, the first time they took the county in 40 years. Now they just amass bigger and bigger margins of victory in FC, along with Arlington County and the city of Alexandria. NoVA resembles SF or Philadelphia, not a southern state.
Gillespie can only win with a very low Dem turnout. I don't see that happening in NoVA. The Dem machine is just too powerful.