Mitt did learn to warm up a little as the campaign season wore on. He told heartwarming stories even if he did not emote very well.
I think he poured on the power too late.
Obviously his greatest improvement was in the first debate. His likability improved because of respect and admiration for his ability, if not necessarily for relatability. But this election was too important to pick a candidate who still had his campaign training wheels on. I still think Newt Gingrich would have pulled this off. He would have had no problem relating to the common, blue collar white guys that stayed home. They would've believed that he was on their side. And he wouldn't have held anything back when criticizing Obama.