I heard Hersch the other day on Fresh Air remark that Bush has turned against Jafari because they believe that if he takes power he will call for a US withdrawal from Iraq. Meanwhile there is a 'new' alliance being talked about between the Kurds and the Sunni in opposition to the Shia. If true this would suggest that ideologically at least the Shia are being cast as anti american and pro Iranian, not to mention all the rumors of Iranian support etc.
Thinking back if you remember Chalabi who is shia went to Tehran at a time when he was being lambasted in the US Press. But perhaps that is nothing more than an attempt to draw Iran into cooperation that failed. The diabolical gambit where you pretend to sacrifice a pawn that you know will probably be refused anyway. Only to take it up later with the knowledge that you never meant to sacrifice it in the first place.