I previously noted that in the modern era of Presidential politics, the Republicans have always gone for the person deemed to be “next in line”. One of the criteria used to determine the person who is next in line is the person who finished 2nd in the previous contested primary season.
There is no similar “next in line” in the Democratic Party. Indeed, 5 of the last 6 Democratic candidates, prior to their first nomination, had never sought the office of President, with the sixth (Al Gore) attempting to get a promotion from Vice President. Yes, Walter Mondale also had served as Vice President, but 1984 was his first and last attempt to become President.
The last person who won the nomination after failing to secure it in a previous attempt and without taking up residence at the Naval Observatory was George McGovern. He finished 3rd in 1968, and used the reforms he came up with to take away the nomination process from the party bosses to become the nominee in 1972. Before that, one has to go back to 1924 and John W. Davis and his nomination on the 103rd ballot after failing to get the nod in 1920. Needless to say, neither recycled candidate won the White House.
Revisions/extensions (1:58 pm 5/10/2008) – The news just gets worse for Clinton if she fails this time around. The Democrats have gone for a previous failure (either in the nomination process or in the general election) five times in the previous century (William Jennings Bryan for a third nomination in 1908, Davis in 1924, Adlai Stevenson for a second nomination in 1956, McGovern in 1972 and Gore in 2000), and lost all five times. Past performance is an indicator of future performance.
R&E part 2 (2:10 pm 5/10/2008) – I forgot to mention Lyndon Baines Johnson and his last-second attempt to get the nomination in 1960. In any case, he did serve as VP and President prior to 1964.