Mondale - too incompetent being part of Carter's presidency
Dole - too old and not viable
Kerry - came the closest, but still seen by midwest Americans as an out-of-touch weak flip-flopping northeast liberal.
Also, GW Bush had a strong floor of voters at 51%. These are the voters that supported Bush in 2000.
I agree with this. Many of the ones who voted for Bush in 2004 who did not vote for Bush in 2000 were swayed by the last-minute DUI revelation, which convinced them to stay home. Some others had a hard time voting against Gore simply because of the obvious economic successes of the Clinton/Gore years. However, the race was going to be a lopsided landslide for Bush until the DUI came out.
Actually, Gore was really a center or center-right Democrat on most every issue other than the environment. And he totally downplayed his environmentalism in 2000. These are the reasons why Nader took 2.7% of the electorate, probably costing Gore the election in NH (and definitely FL).
Yeah, Obama is in a world of trouble. It is hard to see him beating the Republicans at the turnout operation. Anything is possible, especially when you consider the Chicago Way being "vote early and vote often."