As an aside, how many candidates have dropped out because of scandal? Any kind of scandal? I mean, if you watch The West Wing or other such things you would think it happens a few times per cycle just at the presidential level, but I'm remembering Gary Hart and Joe Biden, both in 1988, and...who else?
And getting back to the earlier post, neither was, strictly speaking, about anyone uncovering something from the past. Even at other levels, I'm not thinking of a whole lot of campaigns that end because of a someone uncovering something from the past. There's the Jack Ryan/Jeri Ryan thing from 2004 (but note: it was Ryan's first campaign for public office, so no old staff elsewhere). Granted, there are embarrassing episodes from the past that come to light but don't knock a candidate out, such as Bill Clinton's draft record or George W. Bush's drunk driving, so it's not as if it never happens, but again it may be that these things just don't happen nearly as often as we think they do.