Via Jennifer Rubin, the Cook Political Report thinks Scott Brown has a chance:
At this point, we suspect that the race has indeed closed somewhat and that the result will probably be closer than it ought to be, but we continue to believe that [Republican Scott] Brown has a very uphill struggle in his quest to pull off a Massachusetts Miracle. At the same time, we have a well-earned appreciation for how unpredictable special elections can be even in states or congressional districts that sit solidly in one party’s camp or the other. For that reason, and an abundance of caution, we are moving it from the Solid Democratic column to the Lean Democratic column.
In case you forgot, Rubin reminds us "this is Massachusetts."