So the answer to the question "Can Candidate X represent my district if she doesn't live in the state?" revolves around the definition of "live in."
And the answer to the question "Can Candidate Y represent my district if he doesn't live in the district?" is yes, if he is an "inhabitant" of the state.
The U.S. Constitution requires that a U.S. Senator shall "when elected, be an inhabitant of that state for which he shall be chosen." Ditto, a U.S. Representative.
That's it. Note the noun "inhabitant" not the verb "reside" and certainly not the colloquial "live in."
In 1995, in U.S. Term Limits, Inc. v. Thornton, the Supreme Court (5-4) ruled that "Qualifications Clauses were intended to preclude the States from exercising any [power over Congressional requirements]" and, as a result, the Constitution "fix[es] as exclusive the qualifications in the Constitution." At that time, 23 states had established term limits for their members of Congress; the Supreme Court decision made them null and void.
And in 2000, Dick Cheney changed his voting registry from Texas to Wyoming so that he could run as George W. Bush's vice president. That's because the President and Vice President cannot inhabit the same state, and both men worked and lived in Texas. But Cheney also had a home in Wyoming and had represented the state in Congress.
The Founding Fathers debated -- and rejected -- more explicit residency requirements, according to court records. But remember that back then only landed white men could vote, too.
2008 Residency Controversies
So if the guy running for the U.S. House in your district happens to have his legal residence in another district, like Rep. Tim Mahoney (D-FL-16), it's not illegal. It won't disqualify him. But you should probably vote for another person if you believe your Congressman should reside in the district.
Things are a little murkier with Rep. Robert Wexler (D-FL-19), since he has claimed his Maryland home as his primary residence for four years, in exchange for tax breaks. Does listing his mother-in-law’s house as his residence -- when it's in an over-55-only retirement community and he's only 47 -- really qualify as being "an inhabitant" of Florida? See what I mean about revolving around the definition of "live in"?
Then there's Rep. Christopher H. Smith (R-NJ-4). He is registered to vote in Hamilton Township (NJ) where he rents a townhouse, and he has been a registered voter in the county since 1982.
But Smith, like many Congressmen (and like Wexler), owns a home in Virginia; Smith moved his family with him to the D.C.-area after he was elected to Congress in 1980. But he is reportedly "the only New Jersey congressman who does not own a home in the Garden State, and his daughter attends a university in the Virginia state school system where she is charged in-state tuition." Will his constituents care? I doubt it.
On Tuesday, Smith is facing Democrat Joshua Zeitz, who charges that Smith is either defrauding the state of Virginia or the citizens of New Jersey. Of course, Zeitz -- a self-proclaimed New Yorker -- returned to the States from Britain in 2007; rented an apartment in New Jersey; and began running for Congress. He says he'll decide whether or not to stay in New Jersey after the election.
In Texas, incumbent Rep. Nick Lampson (D-TX-22) succeeded Rep. Tom DeLay (R) in 2006. Lampson served four terms in the U.S. House before Republicans shuttled him offstage through redistricting. However, Lampon's wife is registered to vote in District 2, according to RedState.com. Like Mahoney, it doesn't make you ineligible if you live in another district. (tip)
Of the four, Mahoney and Lampson may be the most vulnerable, as each is a one-term incumbent.
And just like the G.O.P. attacked against Hillary Clinton as a "carpetbagger" when she ran for U.S. Senate from New York, it's attacking comedian Al Franken as a "carpetbagger" even though he has returned to his native Minnesota to run for the Senate. Clearly Franken meets the Constitutional test of "inhabitant," having been campaigning in Minnesota for a year!
So there you have it. Until we amend the U.S. Constitution, residency requirements are in the hands of the voters.