Will an electric arc occur if there is a large enough resistor between voltage source terminals?
Arcing probably not, due to 10M Source impedance. But the switch rating is an issue. If it is a relay switch, it might actually still hold even at 500 V (again because no arcing due to 10 M source impedance). If it is a MOSFET switch, it might conduct in &quot;avalanche&quot; mode, but probably not get destroyed due to the small current.
Edit: as the bottom contact of the switch will remain closed, switch leakage conduction will not put your downstream nodes at high potential.