He attended the public schools in Millerton. He graduated from Fordham Law School, practiced law in New York City, and lived in Jackson Heights, Queens.
During World War I he served in the United States. Army. He resigned his seat on August 19, 1943, to run for the State Senate seat vacated by the resignation of Peter T. Farrell. Downey was elected on November 2, 1943, to the New York State Senate (3rd Doctorate), and took his seat in the 164th New York State Legislature in January 1944.
He was re-elected in 1944, and remained in the Senate until 1946, sitting in the 165th New York State Legislature.
In 1946, he ran for re-election, but was defeated by Republican Charles T. Corey. In December 1951, he was appointed to the New York City Municipal Court, to fill a vacancy.
In November 1952, he ran to succeed himself, but was defeated and left the bench at the end of the year. He died on March 1, 1960, in Boulevard Hospital in Astoria, Queens.
Downey was a member of the New York State Assembly (Queens Company, 3rd Doctorate) in 1937, 1938, 1939-1940, 1941-1942 and 1943. He was a member of the Queens Tax Commission from 1948 to 1951.