In recent years, Tip O'Neill's famous dictum — "All politics is local" — has looked a little shaky. Candidates these days are judged on where they stand on big national issues, while having little recourse to grease the political wheels back home. It sometimes seems that it's only a matter of time before the common wisdom becomes "All politics is national."

And yet voters still expect their representatives to show a local touch. This has expressed itself in novel ways, most notably the outing of lawmakers who don't own an actual home in their home state. Indeed, as elections become nationalized, proving some local connection can be critical to success in a tight race.

Louisiana Sen. Mary Landrieu (D) is the latest to face this line of attack. Landrieu, the scion of a New Orleans political dynasty, apparently lists her residence as a room or apartment in her parents' house.

This is a step up from Kansas Sen. Pat Roberts, who survived a Republican primary campaign in which he was forced to acknowledge couch-surfing in a friend's house on a golf course when he comes back to Kansas.

These revelations follow in the footsteps of former Indiana Sen. Richard Lugar, who had to go to court in 2012 to get on the ballot after it was found that he had sold his residence in the state and just stayed in hotel rooms when he flew in. Lugar won the lawsuit, but lost his primary campaign.

Ironically, in the golden era of local politics, the residency issue was a less potent political weapon. It was fairly common for politicians to move their families to the D.C. area and largely confine themselves there. Depending on the era, travel home was an expensive and time-consuming undertaking.

American voters also seemed to possess a fairly open-minded attitude to political roots. Politicians occasionally moved from one state and ran in another one, including such luminaries as Daniel Webster and Sam Houston. James Shield, a little remembered 19th-century pol, managed to serve as senator from three different states.

However, no one has done the state switch since 1968, when former Texas Congressman Ed Foreman managed to win election in New Mexico. Former Massachusetts Sen. Scott Brown is trying just such a switch this year, running for the New Hampshire Senate seat, but accusations of carpet-bagging have dogged his campaign, and the polls show him trailing his opponent.

In recent decades, the drop in prices and expansion of plane routes has made it easier than ever for elected officials to get back home on the weekend. Lawmakers are also aware of the value of returning home for basic campaigning and maintenance. And some politicians make their disdain for D.C. a point of pride, choosing to sleep in their office rather than rent a place in town.

But local issues are less important than ever in elections. State legislative races are being funded and run on federal issues that have little to do with the office in question — outside the vote for redistricting. The traditional local appeals that built up formidable politicians of the past — namely, the ability to get special funding for their state or district — has fallen out of fashion, especially for Republican primary voters.

Senators who use to boast of bringing home the bacon are now attacked for excessive spending. For example, Roberts voted against a farm bill that would have helped Kansas farmers, in order to bolster his anti-spending bona fides in the Republican primary.

But the need for a connection with the locals hasn't diminished. The result is that politicians need to grasp local issues even as they follow party orthodoxy on key votes that go against interests in the state.

By not having a local residence, politicians are gift-wrapping a powerful attack ad. It is a quintessential problem of optics — there is no clearer line of attack than that the candidate is not "from around here" or that he or she has sold out and moved to Washington. This attack works even if all the candidate talks about are the issues raging in Washington.

So it would behoove all politicians to keep O'Neill's famous line in mind — even if their stump speech would suggest the opposite.