It's all about Operant Conditioning. Reward and punishment.

He switches party affiliation, Dems promise not to sponsor or support a primary challenge against him. Reward.

He spends a week talking about how he's not planning to be a loyal Democrat - i.e., we can't actually count on him for anything - which finishes up with him publicly backing Norm Coleman. Suddenly, he's stripped of his seniority in every committee he's in. Punishment.

Now he's being offered a chairmanship. Reward.

Now we get to see if he has the learning capacity of a lab rat. 

-from Seraph at After Stripping Him Of Seniority, Democrats Throw Specter A Small Bone