Rhetorical question that I'll answer anyway since you asked.
He's done nothing in Mass but rubberstamp Socialist boondoggles, and put liberals on the bench. He openly stated that he's in favor of AWB and state mandates when it comes to healthcare. No concept of constitutionally limited government.
More creeping socialism? No thanks. Incrementalism only works if your opponent is the one giving ground. Fred Thompson is fine. Rudy, Huck, Romney? Nope. Let's leave the creeping socialism to the Dems. Won't tolerate it from our side anymore.
He would move the party left if nominated, and move the country left if elected. Electable? I would prefer he not be. I'm not defining my standards down any farther.
Romney or McCain? If someone put the gun to your head and you absolutely had to choose.