He was a delegate to the 1948 Republican National Convention and to the 1952 Republican National Convention. He was elected as a Republican to the Eighty-fifth United States Congress and to the six succeeding Congresses serving from January 3, 1957 to January 3, 1971. Cunningham voted in favor of the Civil Rights Acts of 1957, 1960, 1964, and 1968, and the Voting Rights Act of 1965, but did not vote on the 24th Amendment to the U.S. Constitution. He lost his bid for renomination to the Ninety-second United States Congress in 1970 to then Douglas County Commissioner John Y. McCollister. He died on December 18, 2003, in Omaha. He was a member of the Episcopalian church and of Pi Kappa Alpha.