In The New York Times, Adam Nagourney writes:

Political comebacks tend to come in two forms. The first is when a party stumbles back into power because of the mistakes by the other side. A classic instance came in 1976, when Watergate enabled Jimmy Carter to win the presidency. The second kind of march back to power, which takes longer but is more enduring, reflects a party’s success in coming to grips with changing conditions — demographic, ideological or both — and in finding a leader who has mastered the new political terrain. Mr. Nixon did this in 1968, and Bill Clinton did it in 1992.

This analysis is faulty.  On the one hand, it overlooks Carter’s initial success at moving to the center after the McGovern debacle.  Four years after the Democrats crashed on the left side of the road, Carter ran as a Bible-quoting, budget-cutting, formal naval officer.  On the other hand, it downplays the incumbent party’s woes in 1968 and 1992.  RN did indeed talk about new issues and policy ideas in 1968, but the  results also reflected the Vietnam War, a calamitous crime wave, and the failure of the Great Society.   And read my lips:  in 1992, the in-party’s problems — a tax increase and a recession — contributed mightily to Clinton’s 43% victory.   And although Clinton ran as a New Democrat, the party as a whole did not change at all.  Congressional Democrats failed to adapt to the times, which helps explain why they lost their majority in 1994.