In 1956, Dwight Eisenhower broke Kentucky's nearly 30 year streak of voting Democratic in Presidential elections. Ike made large gains from his '52 showing in coal country and central KY. Ike's coattails flipped both senate seats, defeating majority whip Earle Clements.
Ike's surprisingly large win in KY was aided by Democratic infighting between new Governor Happy Chandler and Senator Earle Clements. Chandler contributed little to the party's efforts as his longtime rival, Clements, and a Clements ally were the two nominees for US Senate.
Longtime Rep. Bill Natcher saw his closest margin (by far) this year. His journals reveal his shock at the GOP wins and who he blamed. He writes that Ike's handling of the Suez crisis won over many newly enfranchised 18-20 year olds. Interestingly, he alleges mail ballot fraud.
In 1960, Richard Nixon won Kentucky by a smaller margin than Eisenhower. Kennedy's Catholicism and northeastern origins likely hurt him in the state. Race was a large issue in the campaign, and Kennedy lost the support of many Dixiecrats.
Though the statewide margins of 1956 and 60 are similar, there were many regional shifts. Kennedy's largest increases came in Catholic areas, particularly Nelson and Marion counties. Additionally, Kennedy made gains in coal country, even though the region was heavily Protestant.
Nixon made huge gains in the Jackson Purchase region, along with the rural communities along the Ohio River in northern (?) KY. Racism and anti-Catholicism likely drove much of the shift in these once staunchly Democratic counties that would begin to abandon the party.