The leader of a group of local Sunni tribes cooperating with American and Iraqi forces in fighting extremist Sunni militants in Anbar Province was killed by a bomb today, Iraqi police officials said, in a blow to an effort President Bush has held up as a model of progress.

this could swing either way
either obviously destroy the allance of tribes opposed to AQ
OR
entrench and deepen opposition to AQ

Bomb Kills Sunni Sheik Working With U.S. in Iraq - New York Times