Determining a candidate's odds of winning a recount is a function of three parameters. The first parameter is the margin separating the leading and trailing candidates. In Minnesota, this margin is apparently 221 votes -- although it has changed several times since results first came in on Tuesday night (it was originally more than 700), and it may change again before results are finalized this week. But let's assume that 221 is the correct number for the time being.
The second parameter is what I call the Correctable Error Rate (CER). This is the percentage of ballots that were not counted originally, but which will be counted given a hand recount.
The third parameter is the percentage of recounted ballots which are resolved for the trailing candidate -- in this case, Al Franken. It might seem natural to assume that this number is 50.0%, but there is good reason to think that it might not be. More in this in a moment ...
If, over the long run, we expect Franken to win 51% of corrected ballots, his odds of winning the recount may be quite strong -- in fact, he may be the prohibitive favorite depending on the number of recounted ballots ...
http://www.fivethirtyeight.com/2008/11/frankens-odds-of-winning-recount-may-be.html