Sen. Mary Landrieu's Newest Fight Is Over Her Louisiana Residency

— -- Louisiana Sen. Mary Landrieu is the latest Washington veteran being forced to fend off a challenge to her reelection that alleges she is no longer a resident of her home state, but lives in DC.

A similar challenge succeeded in knocking off former Indiana senator Richard Lugar in 2012, despite - or because of - his 35 years in Congress.

Landrieu's office and campaign are fighting back very cautiously.

“I have lived at my home on Prieur Street (New Orleans) most of my life and I live there now when not fulfilling my duties in Washington or serving constituents across the state,” Landrieu said in a statement released to ABC News.

A Landrieu campaign official also noted that both Landrieu and her husband file taxes in Louisiana. Her campaign did not elaborate further.

It is an issue that is increasingly being employed this year against members of Congress who are repeatedly reelected, and spend most of their time in Washington.

Sen. Pat Roberts, R-Kansas, acknowledged to The New York Times that he does not have a home of his own in Kansas, and his primary opponent, Dr. Milton Wolf, has attacked him over it. Rep. Dan Maffei, D-N.Y., has feuded with his Republican opponent, John Katko, over a mention of Maffei’s wife’s work and the couple’s home in the D.C. area.

Landrieu, a Democrat, is already in a race that is considered one of the most closely contested this year and could determine control of the Senate.

Landrieu claims her parents’ home in New Orleans as her principle address, and listed it on her statement of candidacy filed with the Federal Election Commission earlier this year. But the Democrat also lists her multi-million dollar Washington, DC home as her address on other documents, including her filing with the Louisiana Secretary of State’s office when she qualified to be on the ballot last week.

Rob Maness, a tea party candidate in the race, filed a letter with the Louisiana Secretary of State’s office last week calling for an investigation into Landrieu’s residency. He followed up on Friday by submitting written complaints to district attorneys in four parishes, calling on them to object to the Landrieu's qualifications as a candidate. Landrieu’s leading Republican opponent, Rep. Bill Cassidy, has piled on to paint Landrieu as a creature of Washington.

Louisiana Senate Race 2014: ABC News' '14 For '14'

Mary Landrieu's Terrible, Horrible, No Good, Very Bad Week

Mary Landrieu Takes Heat for Spending Public Money on Private Flight

Landrieu maintains that she lives at her parents’ home in New Orleans, of which she is a partial owner under a family trust and where she is registered to vote.

According to the Louisiana Secretary of State’s listed qualifications, a candidate for U.S. Senate must “be an inhabitant of Louisiana when elected.”

The Constitution governs residency requirements, broadly. As Louisiana’s law is worded, it requires senators to “be an Inhabitant of that State in which he shall be chosen.”

The definition of what it is to be “an inhabitant” is a broad one, said Dr. Pearson Cross, the head of the political science department at the University of Louisiana. From a legal standpoint, he said it would be difficult to prove that Landrieu is not an inhabitant.

“Courts have been reluctant to intervene in that and have given a lot of latitude in defining residency,” Cross said. “To say that Mary Landrieu is not a resident is a bit disingenuous given that Senate and Congress have become a full-time occupation and that their work is done in Washington.”

Cross said the issue of Landrieu's residency is a ploy likely to influence voters who are already inclined to vote against Landrieu.

“It will have resonance with some voters who are pre-inclined to believe,” Cross said. “It will probably have little effect on voters who aren’t inclined to believe it. In terms of Louisiana politics, it’s clear that many people, particularly those with national focus, are running against Washington. To the extent that you can tar someone with the Washington brush, it’s an effective campaign tactic.”

This story has been updated.