Despite the headlines that General Petraeus has made for anything remotely negative, the man did a hell of a job commanding Multi-National Forces - Iraq. In a nutshell, the troop increase decreased violence (note: an increase in forces does not equate to an increase in combat).
General Ordierno is faced with a few challanged. He needs to bring and end to the violence between tribes, as well as the violence toward foreign contractors. He also will be responsible for the continued training of Iraqi forces so they're better prepared to deal with future hostilities. He'll be doing allof this with far less troops.
Depending on who gets elected, the new Commander will have to adjust his strategy of leadership accordingly. How do you think the climate of the Iraq conflict will change if Obama is president, and vice versa with McCain.