I did find an article that might have a full answer (or might not), but I don't have time to read it. And, I don't know if the link is going to work. It's a .pdf file:
http://journals.cambridge.org/download.php?file=%2FSAP%2FSAP19_01%2FS0898588X05000039a.pdf&code=1cdcc9c335baf0957fc0936b8a4b398cIn case that doesn't work, Google will turn up the article from the title, Partisanship and Contested Election Cases in the Senate, 1789–2002, by JA Jenkins, Northwestern U.
In a quick brush-over of some of the tables, I jumped to this immediate conclusion: the more redneck jokes one can tell about a state seems to be the primary indicator of how likely that state is to have a contested election. In descending order, the states with the most contested elections include: Louisiana, West Virginia, Kansas, Maryland. However, a large number of states have had five contested elections since their inclusion in the Union, including Delaware, which is not known for its redneck jokes.
Edit: I should add that the paper makes note of another phenomenon: the person who "wins" the first time around keeps the seat over 70 percent of the time. The person causing the trouble appears to have won only twice since 1789 (can that be right?). Much more often the Senate simply votes to vacate the seat, which generally forces the states to hold another election. One could argue that Coleman's primary objective must be to deny Minnesota its representation in the Senate, for he has minimal statistical or historical precedent for pursuing his line of attack to victory.