Why John F. Kennedy's legacy endures

It has been 50 years since President John F. Kennedy's assassination, and he still looms in the public consciousness.

"If we hadn't had a world of photography and film, I'm not sure the memory would be as strong as it is right now, because he did only have three years in the presidency," said historian Doris Kearns Goodwin, author of "The Fitzgeralds and the Kennedys: An American Saga."

At the time, America was feeling optimistic about the world, says Goodwin.

"There was a sense of a mood of destiny in that generation, and when it was cut short, I think there will always be a romantic feeling about it," said Goodwin.

Indeed, several authors – Stephen King and Jeff Greenfield among them – wrote books speculating about what could have been, had Kennedy lived.

"I think it would have been different," said Goodwin. "I'm not sure that JFK would have been able to get the civil rights bill through the Congress. Would he have been able to get Voting Rights bill, Medicare? I think LBJ had a brilliance with the Congress that JFK wouldn't have," said Goodwin.

But Kennedy was more rational than Johnson, added Goodwin.

"It's possible when the war was spiraling out of control, he might have said enough, and he might have cut it short earlier, and that would have made such a difference in the country," said Goodwin. "But we don't know. He might not have."

For more of our interview with historian Doris Kearns Goodwin, check out the video above.

CNN's Edward Meagher contributed to this report.