Candidates who ran a bad campaign and still won?

[Vosem]

Examples of candidates who pissed away large leads, or under-performed dramatically:
Bush '04/'00 (led by a lot in the year before the election, 1999/2003, but had basically lost the advantage to a tie in the summer before the race; not sure if these count)
Clinton '92/'96 (bled to third-parties down the stretch in both races)
Carter '76 (pissed away one of the greatest leads ever recorded in the summer of '76; still won by 2 points)
Nixon '68 (went from leading by a landslide to winning by less than a point)

Hard to say about earlier campaigns, since there was a lot less polling in those days. My impression is that before the 1920s elections tended to be much more static, but examples of candidates who were expected to win dramatically but actually won narrowly, based on my general read of the political environment, included Cleveland's last campaign (1892) and Zachary Taylor's election (1848). In general, this feels like a more common campaign type in modern times.

Obama generally held to the advantages he had, and Trump was actively disfavored for most of the race. The most spectacular bad campaign in recent years was that of Mike Dukakis, though, who went from leading by double-digits over the summer to losing by a full 7 points on Election Day. (Carter 1976 lost a similar amount of support, but he still at least eked it out in the end).