Jenner worked as an elevator operator in the old House Office Building while attending night classes at the George Washington University Law School.

[4] One month after his discharge from the Army Air Corps, Jenner was elected to the U.S. Senate seat that had been vacated by the death of Frederick Van Nuys.

[10][11] Jenner and McCarthy were both part of "a core of isolationist Republicans in the Senate" along with Herman Welker of Idaho and George W. Malone of Nevada.

During the confirmation debate, Jenner and McCarthy formed part of a group of militantly anti-communist Republican Senators that attacked Marshall.

Jenner "delivered a shrill, hour-long attack on the nominee" in which he also disparaged President Harry S. Truman and Secretary of State Dean Acheson.

"[16] Jenner also "denounced and blamed Marshall for the Pearl Harbor defeat and for his role in helping FDR 'trick America into a war,' the extension of lend-lease to the Communist Soviet Union, the 'selling out' of Eastern Europe at Yalta, the loss of China, and the inclusion of an offer of aid to the Soviet Union under the Marshall Plan.

"[16] In 1951, after President Truman dismissed General Douglas MacArthur for insubordination, Jenner gave a speech on the floor of the Senate in which he said: "I charge that this country today is in the hands of a secret inner coterie, which is directed by agents of the Soviet Government.

"[4] Jenner introduced legislation that sought to strip the Supreme Court of jurisdiction "in all the areas where it had interfered with the anticommunist program," a measure that Senator Lyndon B. Johnson maneuvered to oppose.

After leaving the Senate, Jenner practiced law in Indianapolis and was the owner of the Seaway Corporation, a land development company.

William Ezra Jenner died age 76 on March 9, 1985, of a respiratory illness at Dunn Memorial Hospital in Bedford, Indiana.