Immigration was the driving factor behind Cannon’s unpopularity with the district’s Republican base. Despite sporting a near-perfect score from the American Conservative Union, Cannon alienated border security hawks over the past several years with his belief that illegal immigrants should be eligible for certain government benefits.
("The driving factor" - remember that when the spin starts!)
Our friend "An Economist" comments:
Chris Cannon was a key Bush Amnesty proponent for years. At one point he rather foolishly stated "we love immigrants in Utah and we don't care if they are legal or illegal". What is the significance of this election? Hard to say. Tamar Jacoby once wrote that if Chris Cannon was defeated no Congressmen would ever dare vote for Amnesty (roughly). True? Of course, not. However, the defeat of an incumbent (7 term) Congressmen in a primary is rare thing. It won't show up in the national press. However, folks in Washington will notice the forced departure of Chris Cannon.
VDARE.COM presaged Jason Chaffetz' defeat of Cannon here and here.