Lucretia Caldwell Engle, 69, the widow of Sen. Clair Engle (D-Calif.) who was active in campaign organizations and congressional wives groups, died of cancer Jan. 25 at Georgetown University Hospital. She lived in Washington.

Mrs. Engle was a native of Tulare, Calif., and a graduate of San Jose State College. She came to Washington about 1940 and was a secretary to former representative Jack Z. Anderson (R-Calif.) before her 1949 marriage to Engle.

Clair Engle served in the House of Representatives from 1943 to 1959, and then was a member of the Senate until his death in 1964. During the years of their marriage, Mrs. Engle was an indefatigable campaigner and seemingly tireless worker for her husband.

She did volunteer work at his congressional offices, directed much of the flow of his constituent mail, did office work for him in California and campaigned at his side. A pilot in her own right, she and her husband flew throughout his 23-county House district, the old 2nd District, which included about one-third of the state's land area, where she became as familiar a sight as her husband. She also was a prominent figure in Engle's 1958 Senate race.

Although it was determined in 1963 that Sen. Engle had an inoperable brain tumor, he announced his candidacy in early 1964 for a second term in the Senate. Mrs. Engle became the center of a political storm. Many said she had kept the seriousness of the senator's condition from the public, and perhaps the senator himself, and had encouraged him to run for reelection. Stories began to appear, suggesting that an ailing Engle would cost Democrats the Senate seat.

In April 1964, Engle announced he was not a candidate for renomination and reelection to the Senate. In May 1964, Mrs. Engle sent a highly publicized letter to Pierre Salinger endorsing him for the Democratic nomination for her husband's seat. Salinger, the 1964 Democratic nominee, was appointed to the Senate after Sen. Engle's death on July 30, 1964. Salinger was defeated in the 1964 general election by Republican George Murphy.

Mrs. Engle had been active in several social and welfare groups in Washington. She also had been the liaison officer of the Ladies of the Senate and the American Red Cross and was active in the Democratic Congressional Wives Forum. She had been a director of the Congressional Club and a member of the Woman's National Democratic Club and the Florence Crittenton Home Circle. She was a member of Christ Episcopal Church on Capitol Hill.

Her first marriage, to Keith I. Kibner, ended in divorce.

Mrs. Engle's survivors include a sister, Mrs. Robert Goold of Morgan Hill, Calif.