at the same time,the consensus behind Mr.Obama's plan …… at the same time,the consensus behind Mr.Obama's plan (to pull US combat troops out of Iraq) may stem in part from the subsiding violence since Mr,Bush changed strategies and sent more troops (to Iraq) in January 2007, a shift that the new presedent,who opposed that ,did not directly address in his speech. there is a difficult question for me .that is about the structure of the whole sentence.that happens here, "a shift that the new presedent,who opposed that ,did not directly address in his speech."what dose shift mean here?and is it the object to "address",i mean just like the new president didn't directly address the shift in his speech. if not,what roles on grammer does it play in this sentence? could you explain it for me ,thinks!