The theory is that without Iraq in 2003, Bush wouldn't have as much of a platform to run on re-election in 2004. His 90% approval rating following 9/11 would have probably dropped to about 40-50% as people begin to realize his ineptness in preventing the attacks before 9/11 and his inability to bring the top leadership of Al Qaeda to justice in a quick manner.
Instead, with the Iraq diversion and the capture of Saddam before the end of 2003, Bush was able to give off the image of a strong President who could defend America's interests abroad against terrorism (even though the evidence was shaky at best) and was able to defeat John Kerry in 2004, whom he was able to portray as a Vietnam dodger.
Without Iraq, was it possible for President Bush Jr. to have successfully won re-election in 2004 in your opinion?