Arthur Schlesinger liked to defend his decision during the 1960 campaign to defect from the Adlai Stevenson camp to the John F. Kennedy camp in terms of the idea that Stevenson had a discomfort with the idea of power that, while arguably admirable in some respects, was fundamentally inconsistent with the realities of political leadership. I've seen analogies to this situation applied to the Clinton-Obama race several times. Available on the internet is this post from George Packer which lays the analogy out in some detail, and this interview with Sean Wilentz in which he refers to it more elliptically but explicitly draws the conclusion that Clinton is like Kennedy and Obama is like Stevenson and that this is the reason to support Clinton.
This doesn't make a ton of sense to me. For one thing, Schlesinger's morality play in which Stevenson is an honorable man but maybe too honorable to beat the GOP in '52 and '56 whereas the slightly seemier Kennedy gets the job done in '60 is a pretty weird interpretation of the politics of the 1950s. In 1952, the Democrats had been in the White House for 20 years, Harry Truman's approval ratings were in the low twenties, and the Republican nominee was one of the most respected and popular men in the world. What's more, instead of taking advantage of Truman's unpopularity and his personal popularity to try to revive American conservatism, Ike just ditched all of the GOP's less popular positions and ran, won, and governed as a moderate. Under the circumstances, Stevenson was doomed.
Meanwhile, the reality of the Kennedy Administration -- as opposed to the Myth of Camelot -- is precisely what makes people leery of Clinton. A 50%+1 win followed by a domestic agenda that goes nowhere in congress and a drift toward foreign policy disaster driven in part by a unshakeable fear of looking soft on defense.