What's Wrong With Senator Grassley?

Senator Grassley used to represent one of the more pragmatic voices in the Senate.  I watched as he abandoned the working relationship he had with Democratic Senators like Max Baucus and refused healthcare legislation to get a vote on the senate floor.  I've watched as he refused to allow a vote on Background checks and a host of other issues.  Now he wants to stall a vote on Immigration reform.  Why has the Senator become a dependable bulwark to stop legislation from coming to the Senate floor?  The change occurred during healthcare reform.  He was working on a bipartisan bill but eventually decided to protect his seat rather than legislate, in the face of growing tea party opposition.  To make sure that they knew he was another shrill voice they could count on, he referenced Sarah Palin's distortions about death panels and said he wasn't going to let anything happen to grandma.  The reality is that Senator Grassley doesn't legislate anymore, he protects his seat.  He doesn't allow votes to come to the floor because he is more interested in putting his finger to the wind before he takes his positions.