Ezra offers up some insight:
This is the final year that Grassley is eligible to serve as ranking member -- the most powerful minority member, and, if Republicans retake the Senate, the chairman -- of the Senate Finance Committee. His hope is to move over as ranking member of the Judiciary Committee, or failing that, the Budget Committee. But for that, he needs the support of his fellow Republicans. And if he undercuts them on health-care reform, they will yank that support. It's much the same play they ran against Arlen Specter a couple of years back, threatening to deny him his chairmanship of -- again -- the Judiciary Committee. It worked then, and there's no reason to think it won't work now.
This is interesting, especially because I never factored pressure of any kind into Grassley's outbursts. I just wrote him off as crazy.