The U.S. is going to attack Iran this year. The timing will be set for maximum impact on the 2006 U.S. Congressional elections.
For extra credit: not a prediction, but I wouldn't be surprised by the use of tactical battlefield nukes. One important advantage is that this may help to smoke out Democratic opposition, or in the alternative make them more complicit.
Final point to keep in mind: this would lead to much greater protests than invading Iraq (potentially another advantage). Bush claims unlimited Commander in Chief powers to act domestically as he sees fit to prevent harm to the war effort.