Silver, G. Elliot Morris of 538, and several other forecasters have a system built into their models where “no state is an island”. Essentially, trends in polled neighboring states have been found to bleed through the borders and indicate something about what’s happening in an unpolled state.
Virginia’s lean in Silver’s analysis today is certainly being influenced by recent state-level polls in Pennsylvania, North Carolina and likely Ohio. And it’s not necessarily going by raw red/blue status. Ohio might today still poll as a comfortable Republican win, but if Trump is today getting (say) ~55% of Ohioans instead of (say) ~59% in recent past polling, that pro-Harris trend in Ohio will count some in scoring Virginia “bluer”.