Tim Cahill's biggest mistake was running as an independent. Generations of Massachusetts political wisdom tells us that if you're a "regular" Democrat taking on a reformer, you do it in the primary -- especially if you have an Irish name. You run as an independent when you're going after unenrolled voters, but they aren't Cahill's base.
Here's another piece of old-time wisdom: If the opposing party is split, that's good for you, so just let them fight it out. The Republican governors evidently don't know this.
If Patrick can pull this out based on superior political savvy, what would that say about the other guys?