Election 2008
McCain ran a terrible campaign. He didn't do a good job of defining himself; the thrust of his campaign was to associate Obama with unsavory characters. Poor strategy: (i) many of us instinctively ignore negative political ads, and these were fairly stereotypical in that regard, and (ii) while a good portion of Americans do care about that sort of thing, they were mostly already in the McCain camp to begin with.
Of course, McCain's disastrous blunder was his choice of Sarah Palin as Vice President. She clearly appealed to the Republican base, and appalled everyone else. The killer was the meta-effect: you didn't want to vote for any ticket involving Palin, and you were scared to vote for someone who either thought she was competent to run the country, and/or didn't really bother to carefully vet someone for such an important position. Yikes.
Who knows how well Obama will govern, but I look forward to him rolling back some of the more damaging actions of the Bush reign, and restoring America's honor and moral strength.