The "What If?" game of history is never more fun than when played using real-life moments in our history. What if Lincoln had turned down an invitation to Ford's Theater that night of April 14, 1865, and Gen. U.S. Grant had gone instead? What if the rain showers that had been sprinkling over Dallas had continued for a few more hours on Nov. 22, 1963?

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In the case of President John F. Kennedy, historians and authors point to many moments where a slight change of events could have resulted in Kennedy making a successful campaign trip to Dallas without incident. But then what? How would the United States be different now if Kennedy had survived?

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Journalist and television commentator Jeff Greenfield pondered this idea in his new book "If Kennedy Lived: The First and Second Terms of President John F. Kennedy."

Greenfield's alternate history begins when Secret Service agents decide not to remove a protective clear plastic rain bubble on the president's limousine for the ride from Love Field to downtown Dallas. In Greenfield's version, Oswald's bullets strike the shell, but only manage to wound President Kennedy.

"Everyone assumed it would rain all weekend," Greenfield said. "The clearing of the skies has been a part of the speculation or talk about what happened for almost 50 years."

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Greenfield carefully lays out a different path in which Vice President Lyndon Johnson finds himself under investigation for financial improprieties and is dropped from the Democratic ticket in 1964. Kennedy is re-elected over GOP nominee Barry Goldwater, but instead of escalating U.S. involvement in Vietnam, Kennedy plays it more cautiously and pulls out during his second term.

As for Russia, Kennedy decides to make up for a disastrous first summit with Soviet Premier Nikita Khrushchev by making an official visit to Moscow, hoping to reduce Cold War tensions.

Greenfield also sees Kennedy opening up relations with China years before President Nixon's visit in 1972. He believes Kennedy could have passed civil rights legislation using black military veterans as a political tool against opponents, mostly southern Democrats.

Another author (one of more than 100 out with JFK books this fall) believes President Kennedy would have been less successful than Johnson was when it comes to the "Great Society" social programs of the mid-1960s.

President Kennedy in March 1961.Corbis

"After the (1964) election, Kennedy would have gotten the civil rights bill passed," said Larry Sabato, pundit and political scientist at the University of Virginia and author of "The Kennedy Half Century: The Presidency, Assassination and Lasting Legacy of John F. Kennedy."

"I doubt it for the Voting Rights Act or the Open Housing Act in 1968. Kennedy had to be dragged to civil rights."

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Kennedy's efforts in domestic policy and foreign affairs may have been sidetracked by his personal peccadilloes, namely his insatiable appetite for women.

Kennedy reportedly had affairs with prostitutes, a mobster's girlfriend, White House interns and Georgetown socialites while in office. The Secret Service was worried that Kennedy's behavior opened him up to spies or potential assassins. And could these affairs have come back to bite him as blackmail during the 1964 campaign?

Sabato thinks not. In those days, the Washington press corps was considered part of the White House team, and Kennedy knew how to play them.

"There were so many women of all types," Sabato said. "Sooner or later it would have come out. My bet is after the second term."

Jeff Greenfield notes that as a senator in the late 1950s, Kennedy's affair with a young Capitol Hill staffer was tape recorded by a couple in whose house the young woman lived. Despite the couple's best efforts, only a neo-Nazi propaganda magazine printed the allegations, Greenfield said.

"Today, they would have posted it to YouTube," he said.

Greenfield's book ends with a plot twist involving the president and his wife, Jacqueline. Still, he believes the turmoil that rocked American society in the late 1960s may have been muted had Kennedy remained alive and in office.

"It would have been a much less grim country," he said.