I'm not sure I'd go with McCaskill or Reid, seeing as they both, especially Reid, manipulated the republican primaries to get the candidate they wanted. So it was more skill than luck. Chris Coons wouldn't be a bad choice.
Yeah, this is the correct answer. Coons went from the status of complete nobody to that of future US Senator by virtue of events no rational mind could have foreseen.
I'm sure... If Coons ran against Castle in 2006, 2008 or even 2012, given how blue Delaware has become, I'd probably bet on Coons winning, (Which is probably why Castle didn't run in any of those years)