Harry P. Cain, 73, a former senator from Washington state, died Saturday at his home.

Mr. Cain, who was mayor of Tacoma but took a leave of absence to serve as an Army colonel in Europe during World War II, unseated Sen. Hugh B. Mitchell in 1946.

The former banker was nominated to the Senate by state Republicans while he was serving in France. After gaining the Senate seat, Mr. Cain became a strong supporter of the late Communist-hunting Sen. Joseph McCarthy and was known for his outspokeness during his single term in office. In 1952, he was defeated for reflection by sen. Henry M. Jackson (D-Wash).

A former Yale political science professor, Mr. Cain was a member of the Subversive Activities Control Board in the 1950s. In this position, he was a sharp critic of what he regarded as injustices perpetrated in the name of national security.

In 1956, the year he resigned from the Subversive Activities Control Board, he moved to Miami, where he became a vice president of a savings and loan association.

He did not give up politics. In 1962, in South Florida, he was named to the metropolitan Dade County Commission. There he sponsored the resolution declaring the county bilingual. He also led a bitter campaign that resulted in a local law against smoking in elevators and public buildings.

"If I had my way the only place where consenting adults could smoke would be in the shower," said Mr. Cain, a reformed two-pack-a-day smoker.

Mr. Cain lost his seat on the commission in 1976, but he was still in the public arena last week, making a fiery speech before the commission in favor of a police review board.

Mr. Cain was born in Tennessee but moved to Tacoma as a child. He is survived by his wife, Bonnie, two children, Henry P. II, of Potomac, Md., and Mrs. Robert Tingstad of Tacoma, and eight grandchildren.