Israeli policy during the occupation is responsible for Hamas, and it existed before W had any foreign policy influence.

Blaming Bush for Hamas because he was somehow responsible for the elections happening is stupid. The elections happening was a good thing. Fatah stupidly rejecting the idea of a national unity government was a bad thing. Israel deliberately seeking to assure a Hamas victory by interfering with campaigning, and voter registration, conducting a targeted campaign of arrests of Palestinian politicians, and doing everything possible to make the Fatah-led PA look weak, complicit, and corrupt in Israel's favor in the immediate runup to the elections was horrible -- but predictable given the entire history of Israel actively promoting Hamas, from its founding, as a tool to divide Palestinians and assure that there was a public face of opposition less sympathetic to, particularly, the population of Israel's Western Allies (particularly the US) than the more secular nationalists of the PLO during the height of occupation, and Fatah as a political party once there was an entity to have political parties.