In 1966, Blackburn was elected as a Republican to the Ninetieth Congress, having narrowly defeated freshman incumbent James MacKay by 360 votes: 55,249 (50.2 percent) to 54,889 (49.8 percent). In that same election fellow Republican Bo Callaway challenged the Democrat Lester Maddox, a strong segregationist from Atlanta, in the 1966 gubernatorial race.
In 1966, Blackburn was elected to the Ninetieth Congress as a Republican after narrowly winning against James MacKay by 360 votes. Concurrently, fellow Republican Bo Callaway challenged Democrat Lester Maddox, a prominent segregationist from Atlanta, in the same year's gubernatorial election.