Look at what they tell military people, it is where you consider your permanent residence. If you own property and lived in Indiana before the military but in you get transferred to California for 8 years, you can still vote in Indiana if you consider that Indiana property your permanent home. But if you change your official residence to California, you can't revert back to Indiana without moving there.
Ensuring Service members, their eligible family members and overseas citizens can vote -- from anywhere in the world.
www.fvap.gov
If Lugar considered his Indiana home his permanent residence, it fit.