Over on Eschaton, Atrios links to
Is the senator an 'inhabitant' of Pennsylvania?, an article proposing that Rick Santorum is not a resident of the state which he represents, which is a violation of Article I of the US Constitution, which requires a representative to be a resident of the locale he or she represents.
Well, the article says,
Rick Santorum last won election in November 2000, when he owned the house at 111 Stephens Lane in Penn Hills plus a house in Virginia. Where he was an "inhabitant" at the time only he can say.
Actually, that's quite true, if my supposition is correct.
I'm guessing that the term resident or inhabitant is what in law school we refer to as domiciliary. Is Senator Santorum's
domicile in Pa or Va?
You can own lots of residences, but only have one domicile. That is your "permanent residence", so to speak. Your true home base. The place you do not plan to leave. You only ever have one of those at a time, and when you move from one state to another (like I did, recently), you might be construed as still being domiciled in the previous state, even though you're living day-to-day in a different one, unless you make it clear - by word or deed - your intention to put down roots and stay in the new locale.
Ways to show that intent? That varies from case to case and state to state. From anecdotal data, I hear Alaska relies heavily on voter registration as an indicator of domicile. From my casebook on Civil Procedure, New Hampshire appears rather fond of voter registration, business incorporation and activities, and where you file your taxes. (Voter registration is nice because you're only supposed to vote once, in one place, and that seems to parallel the whole 'domicile' concept.)
Mostly, though, if you say so, well, you're kinda presumed to be more aware of your intent than anyone else.
Senator Santorum could have almost no contacts at all with Pennsylvania, and still be domiciled there, if he hasn't moved his domicile elsewhere. You're always domiciled somewhere, even if it's not where you are at the moment.