Ezra Klein is, as usual, making lots of sense:

...all observers agree that flattening Gaza has pushed Hamas back onto its hardline haunches. I don't know what happens to Hamas in some alternative reality where they are elected, fight with Fatah, take power, and then Israel doesn't blockade Gaza and the U.S. doesn't cut off aid. Maybe everything is the same. Maybe it isn't. Maybe the 8 percent that wants to be a popular government more than an eschatological remnant becomes 17 percent. But in the reality we live in, the blockade and the aid cutoff ensured that Hamas would remain radical. Destroying their governmental infrastructure ensured that the guys who make missiles and not the guys who are trying to figure out agricultural policy will chair the floor at the next general meeting. And more than that, it ensured that the Palestinian population that suffers beneath Israel's blockade will be ripe for Hamas's theology of a better tomorrow, and a divine ally, and an eventual victory. The concrete appeal of cross-border commerce with Israel can only contend with the emotional resonance of death to Israel if the people of Gaza realize that they're benefiting from the former and getting nothing for the latter.

He also links to this interesting post on Salafist elements in Hamas.