Coleman is considering breaking with the president on Iraq, I don't think he would consider doing such if he didn't felt he was in peril.
Every Republican is considering doing that right now. Most of it has to do with the simple fact that the Republican base is starting to turn pessimistic on Iraq.
Early in this year, I predicted that Bush would probably have until November or December of 2007 to do something before the situation would become untenable and the troops would be removed from Iraq.
I am now thinking I might have overplayed the call a bit. The situation will probably become untenable by September 2007 and that is when the switch will occur. Probably by April of next year, the number of US troops in Iraq will be down to about half what they are now and the WH will be trying to force partition on the Iraqi government. Meanwhile, Turkey, Saudi Arabia and Iran will naturally be massing forces to try and protect their own interests as the US presence dies down.