Kennedy wasn't particularly liberal you know, he was very moderate.
True, and back then the Democratic Party was the party of white people in the South. This was
before they took a brave stand against racial discrimination and, as LBJ said, gave the South away to the republicans. In 1960, Kennedy won GA 63-37.
Look what had happened in '64 (Goldwater 54/Johnson 46):
And in '68 (Wallace 43/Nixon 30/Humphrey 27):
And in '72 (Nixon 75/McGovern 25):
Then, of course, GA Governor Jimmy Carter won the state in '76 and in '80, with the support of around half of the white population. Clinton also won it in '92. The conclusion is there's a chance GA will vote for a Democrat, if he's moderate and from the South. But after 1960, they seem to have been allergic to more liberal Democrats from the North (Humphrey, McGovern, Mondale, Dukakis... Kerry).