Cathy Long, a Louisiana Democrat who won her husband’s U.S. House seat after his death in 1985 and served one term, died Nov. 23 at an assisted-living center in Chevy Chase, Md. She was 95.

The cause was dementia, her family said.

Mrs. Long beat three competitors with 56 percent of the vote in 1985, with a 2-1 margin over the second-place finisher for the seat held for 16 years by her husband, Gillis Long. The central Louisiana district encompassed Baton Rouge, the state capital.

“It was a challenging time. She had two weeks to decide whether or not to run for his seat,” said her son, George Long. According to her family, Mrs. Long was encouraged to run by Rep. Lindy Boggs (D-La.), who had won her husband’s seat after his plane disappeared in Alaska in 1972.

Gillis Long, a distant cousin of the influential Louisiana politicians Huey and Russell B. Long, was first elected to Congress in 1962. He lost in the next election before being voted back into office in 1972, holding the seat for seven straight terms before his death from a heart ailment on Jan. 20, 1985.

Mrs. Long had advised him and campaigned on his behalf, after previously working for Sen. Wayne Morse (D-Ore.) and Rep. James G. Polk (D-Ohio).

“I don’t have to start from scratch,” she told the Associated Press after her husband’s death. “I already know how Congress works.”

She sought to carry on his work in Congress — maintaining a liberal voting record, working to provide aid for Nicaraguan refugees and voting for sanctions against South Africa for its apartheid system — and did not seek reelection.

Mary Catherine Small was born in Dayton, Ohio, on Feb. 7, 1924. She graduated from high school in Camp Hill, Pa., and joined the Navy at 20 during World War II, serving at a Navy hospital in Corpus Christi, Tex.

The Longs met at Louisiana State University, where both enrolled after the war. They married in 1947, and Mrs. Long received a bachelor’s degree the next year.

In one of her early campaign experiences, Mrs. Long rode across the state with former governor Earl K. Long — her husband’s cousin — while he was running for Congress. He won a Democratic primary runoff and was preparing to run unopposed in the general election when he died in 1960. His death prompted Gillis Long to move the family back to Louisiana to establish residency so he could run for the seat in 1962, George Long said.

Mrs. Long campaigned for the Equal Rights Amendment and worked in the 1960s to promote the Special Olympics. More recently, she fed homeless people and tutored reading at the ­Washington organization Miriam’s Kitchen. She was also a swimmer and scuba diver and, at 60, went parasailing over Acapulco, Mexico.

In addition to her son, survivors include a daughter, Janis Long.