LOS ANGELES -- Jesse Unruh, 64, the treasurer of California since 1975, the speaker of the California State Assembly in the 1960s, and one of the most highly respected Democratic politicians in the United States, died of cancer Tuesday night at his home in Marina del Rey.

Mr. Unruh may be best remembered for his seven years as speaker. He modernized the state assembly, concentrated unprecedented authority in the speaker's office, sponsored progressive legislation and played a key role in national politics as a supporter of the presidential campaigns of John F. Kennedy and Robert F. Kennedy.

He never attained the post he most coveted: governor of California. He was defeated for that office in 1970 by Ronald Reagan, then the Republican governor of the state.

President Reagan praised Mr. Unruh yesterday as a man with "a deep and abiding dedication to the causes in which he believed." The president added, "We knew each other for many years, and I always respected his devotion to the state of California and to the people he served. Nancy and I are saddened by Jesse's death and extend our deep sympathy to his family."

As state treasurer, Mr. Unruh won wide praise in the financial world for his aggressive management of California's $15 billion in securities. Institutional Investor magazine said he "may be the most politically powerful public finance officer outside the U.S. Treasury" and put him at the top of its list of the 10 savviest municipal borrowers in the United States.

As speaker, Mr. Unruh had transformed a part-time, ill-informed legislature that most frequently rubber-stamped the governor's wishes into one that did its own research with a professional staff of consultants and enacted its own agenda, including civil rights and education reforms personally written by Mr. Unruh.

He led the portion of the California delegation supporting. John F. Kennedy at the 1960 Democratic Convention in Los Angeles. Eight years later, he directed Sen. Robert F. Kennedy's successful California primary campaign, and was near the New York senator when he was assassinated.

Mr. Unruh's intelligence and ability were widely recognized. But many raised questions about his methods. A man of gargantuan appetites who was known as "Big Daddy" and who once weighed 290 pounds, he contributed to the doubts by verbal excesses.

He confessed that even his sense of humor sometimes hurt him politically. When visitors to the assembly chamber asked which desk was his, he used to reply that "they're all mine."

Jesse Marvin Unruh was born in Newton, Kan., on Sept. 30, 1922, the last of five children of Isaac and Nettie Unruh. His parents, German Mennonites whose parents and grandparents had emigrated to escape religious persecution, moved to Texas when he was 7.

His father was an illiterate sharecropper and Jesse Unruh never lost his working-class edges, despite having become wealthy and influential. In the 1960s, during the period of student revolt, he expressed his aversion to "flower children," remarking that to him going barefoot was "a badge of shame."

Mr. Unruh attended the University of Southern California. He served with the Navy in the Aleutians during World War II. While waiting to ship out, he met and married Virginia June Lemon, daughter of a Los Angeles police officer who was visiting in Corpus Christi, Tex. That marriage ended in divorce. In 1986, he married Chris Edwards, a longtime companion.

In 1954, on his third try, he was elected to the assembly from his Inglewood and southwest Los Angeles district. Once in the legislature, he made shrewd alliances and rose steadily. He was elected assembly speaker in 1961.

At the outset of his legislative service, Mr. Unruh vowed never to take money from the lobbyists who frequently dominated the assembly. But he wrote later that he and some like-minded colleagues came to realize that legislators who did not take this money often accomplished little and found that it was hard to get elected and take political control without lobbyist money.

"So, stilling our doubts and scruples, we began to play the dangerous game of taking money from would-be corrupters -- to elect men who would fight corruption," he wrote.

He calculated well. The friends he was able to elect with the money he got from the lobbyists eventually helped him become speaker. And as speaker, and even before, he was able to secure passage of landmark legislation relating to civil rights, consumer protection, election reform and management of the state budget.

Mr. Unruh's 1970 bid to unseat Reagan from the governorship fell 501,057 votes short. In 1973, he ran for mayor of Los Angeles, coming in third behind victor Tom Bradley and the incumbent, Sam Yorty.

In 1974, he was elected state treasurer. Many thought the office a powerless one, yet in a short time Mr. Unruh converted it into an influential seat of control over the investment of billions of dollars of state funds. He maintained close relations with the legislative leaders and the two governors under whom he served.

In addition to his wife, survivors include one daughter and four sons by his first marriage and one grandchild.