Elmer A. Benson, 89, who served a two-year term as governor of Minnesota in the 1930s and also served briefly in the U.S. Senate, died March 13 at Mount Sinai Hospital here. He had pneumonia and had suffered a stroke.

Mr. Benson, who described himself as a radical in politics, lived most of his life in Appleton, Minn., where he was a successful banker. He was the state banking commissioner in 1935 when Gov. Floyd B. Olson appointed him to serve the 1 1/2 years remaining in the Senate term of Thomas D. Schall, who died in a car accident.

In 1936, Mr. Benson returned to Minnesota to run for governor and won a landslide victory. In 1938, he was turned out of office by the largest margin ever, receiving just 34 percent of the vote against Republican Harold Stassen, who later became a perennial presidential candidate.

In the years that followed, Mr. Benson lost two other statewide contests. He split with Hubert H. Humphrey and abandoned the Democratic-Farmer-Labor Party he helped create by merging Farmer-Laborites with Democrats. In 1948, he backed Henry Wallace's Progressive Party in the presidential election.

In a 1983 interview with the Minneapolis Tribune, Mr. Benson said he wanted to be remembered as an unreconstructed radical.

"I can't imagine anyone changing his philosophy," he said. "I never have."

Although the 1937 legislature gave Mr. Benson little of what he sought, many of his proposals became law during the following 40 years -- property tax relief for homesteads; higher income-tax rates for high-income individuals and corporations; mandatory workers' compensation coverage for employes; a state civil service system; expanded state aid for schools, financed by income taxes; party designation for legislators.

Mr. Benson, who lived in Bloomington, is survived by his wife, Frances, a son, Tom, and a daughter, Lois.