In Washington, Sen. Mary Landrieu lives in a stately, $2.5 million brick manse she and her husband built on Capitol Hill.

Here in Louisiana, however, the Democrat does not have a home of her own. She is registered to vote at a large bungalow in New Orleans that her parents have lived in for many decades, according to a Washington Post review of Landrieu’s federal financial disclosures and local property and voting records.

On a statement of candidacy Landrieu filed with the Federal Election Commission in January, she listed her Capitol Hill home as her address. But when qualifying for the ballot in Louisiana last week, she listed the family’s raised-basement home here on South Prieur Street.

The New Orleans house, which Landrieu claims as her primary residence, is a new flash point in one of the most closely contested Senate races in the country. Republicans are considering taking legal action to question Landrieu’s residency in the state, arguing that since winning her seat in 1996 she has become a creature of Washington.

For Landrieu, there are hazardous parallels to other recent cases in which residency questions have dogged incumbents. Former senator Richard G. Lugar (R-Ind.) lost reelection in 2012 after reports that he stayed in hotels when he returned to Indiana, while Sen. Pat Roberts (R-Kan.) is drawing flack this year for not having a home of his own in Kansas and listing a donor’s house as his voting address.

“I have lived at my home on Prieur Street 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 Thursday.

The house in the New Orleans neighborhood of Broadmoor is the primary residence for the senator’s parents, Moon and Verna. The other day, Moon Landrieu, 84, the family’s patriarch and this city’s former mayor, was on the front porch tending to the plantings.

Verna Landrieu jointly owns the house with Nineland Partnership, a limited liability corporation set up for the family’s estate planning. Mary Landrieu, 58, and her eight siblings, who grew up in the house, have equal stakes in the partnership, campaign officials said. The home, set on a corner lot, is valued at $297,400, according to Orleans Parish tax assessment records, which do not list the number of bedrooms or other living space details.

On the blocks surrounding the house this week, blue and yellow “I’m With Mary” campaign signs were visible in many yards. But several residents said they had not seen Landrieu in the neighborhood recently.

The home where Sen. Mary Landrieu (D-La.) is registered to vote and where her parents, Moon and Verna Landrieu, live in New Orleans, La. (Philip Rucker/The Washington Post)

“I don’t think she lives there,” said Fontaine Wells, 65, pointing at the Landrieu home. “She might come visit, but come on now — she lives in D.C. I don’t think I’ve ever seen her.”

Still, Wells added, “I don’t hold that against her. . . . She knows our issues, she knows the problems we have.”

Michael Fitzgerald, 61, has lived around the corner from the Landrieus for three decades. He said he sees Moon and Verna Landrieu regularly, as well as Mitch Landrieu, Mary’s younger brother and the city’s current mayor, who lives in a home he owns nearby.

“They’ve been very good neighbors,” Fitzgerald said. “On Election Day, [Mary] is seen at our polling place accompanying her parents.” He added, “I have not seen her lately. . . . She’s been in the Senate for — I’ve lost count — 16 years? 18 years?”

Landrieu’s leading GOP opponent, Rep. Bill Cassidy (R-La.), said the senator has “chutzpah” to claim her parents’ home as her legal residence.

“Let’s call it what it is: She doesn’t live in New Orleans,” said Cassidy, who owns a home in Baton Rouge and a condominium in Washington. “She has an address she uses for voting purposes. . . . She literally no longer lives here. She belongs in Washington, D.C. She just chooses Louisiana to get reelected.”

The Landrieu siblings’ Nineland Partnership also owns a house in Slidell on Lake Pontchartrain, about 30 minutes away. The two-story raised home, which includes a boat dock, is valued at $504,530, according to St. Tammany Parish tax assessment records.

Landrieu herself owns two separate plots of undeveloped land down the street, which records show are valued at $110,000 and $150,000. But there is no record that she or her husband, Frank Snellings, personally own a home in the state.

In 2002, Landrieu and Snellings purchased a vacant lot in Washington on East Capitol Street and built a 5,247-square-foot home with five bedrooms and four bathrooms. The home, which is owned by Snellings, was valued at $2.5 million this year, according to D.C. tax assessment records. He does not receive the homestead tax deduction, the records show; the couple pay income taxes in Louisiana, according to the campaign.

Landrieu frequently hosts fundraisers for her campaigns and for other Democrats at the Capitol Hill house. Snellings, a former elected official in Monroe, La., has worked for the past decade as a real estate agent in Washington for Coldwell Banker. On his Web site, Snellings writes that his family “moved to D.C.” in 1997 and that he specializes in selling homes in the Capitol Hill, Penn Quarter, Georgetown and upper Northwest neighborhoods.

In the Senate, Landrieu has advocated for the District on various issues and has talked publicly about life in Washington. In a 2012 appearance, she said Capitol Hill was “such a special neighborhood.”

“I really can appreciate the life that we live on the Hill,” Landrieu told neighbors gathered at Hill Center D.C. “Of course, I still have a residence in Louisiana, but we’ve raised our kids here.”

Landrieu’s teenage daughter, Mary Shannon, now lives at the family’s New Orleans home and attends school in the city, according to a person close to the family, who asked not to be identified in order to discuss personal details.

After Landrieu officially filed for reelection last week, Republican opponent Rob Maness wrote to Louisiana Secretary of State Tom Schedler (R) asking him to investigate her residency status.

Louisiana’s Election Code states that a U.S. senator must be “an inhabitant of Louisiana when elected.” Schedler’s spokeswoman, Meg Casper, said the secretary of state’s office does not adjudicate residency, which must be challenged in court or by a prosecutor. The deadline for a legal challenge in Landrieu’s case is Friday, seven days after she formally filed her candidacy paperwork, Casper said.

Maness, a tea party-aligned insurgent, said in an interview that he is considering legal action.

“A U.S. senator shouldn’t be living with their parents,” Maness said. “She’s got plenty of good pay, she’s employed, but she says she’s living with her parents? . . . It’s time for one of us from the state of Louisiana to go fill this seat.”

But the Landrieu campaign provided a memo from two of its lawyers, Marc Elias and Joseph Wenzinger, arguing that “there is no legitimate question” that Landrieu satisfies the residency requirements for her seat. “She is not disqualified simply because she maintains a residence in the District of Columbia in order to serve Louisiana,” the lawyers wrote.

Robert Mann, a professor of political communications at Louisiana State University, said the Landrieu family name is so ingrained in Louisiana politics that “no one will think that Mary is not a Louisianan.”

“Saying Mary Landrieu is not really a resident of New Orleans, doesn’t really live in New Orleans — I don’t think will go very far,” he said. “Nobody but the most partisan Republican will grab that flag and run with it.”

Part of what has made Landrieu competitive in a state with deep hostility toward President Obama is her record of delivering federal resources to a poor state and her advocacy for the oil and gas industry.

For decades, home base for the Landrieus has been Broadmoor — an eclectic, middle-class neighborhood located in Uptown, between downtown and the Garden District. The failure of levees during Hurricane Katrina in 2005 left Broadmoor flooded with about eight feet of water. Most homes were damaged. Those with raised basements, like the Landrieu home, fared better than the rest.

In the years since, the neighborhood has been rebuilt and is now a post-Katrina success story. Moon Landrieu was particularly active in the rebuilding efforts, said Kelli Wright, who has lived in Broadmoor since 1988 and is president of the Broadmoor Improvement Association.

But Mary Landrieu, who was instrumental in obtaining Katrina funds for the state, was not personally involved in the neighborhood’s recovery, Wright said.

“Is Mary’s address the Landrieu’s family home?” Wright asked. “I don’t know where she lives. I’ve never seen her around the neighborhood. It doesn’t mean she’s not here, but I haven’t seen her. We see Moon, we see Verna, we see the mayor.”

Alice Crites in Washington contributed to this report.