The betting here is that Haslam is too afraid of his party's base to follow Scott and the rest of the growing number of Republican governors who can do the math and recognize the obviously overwhelming benefits to their states. If he bucks the base, it'll be the first time. Even if he does, then he'd have to fight to win the legislature's approval. Haslam didn't become "the GOP star you've never heard of" by fighting with wingnuts, or anyone else for that matter.
Update: In this week's MetroPulse, Frank Cagle calls Haslam's Medicaid decision "a real test on whether the Republican majority can govern responsibly or whether a minority of loud members will be allowed to rule. It will also be a test to see if Gov. Bill Haslam will have the courage to step up."