Tlar: It is my belief that the coalition has held back on a nomination between Mahdi and Chalabi because they are still hoping to convince the SOL to un-nominate Maliki and pick one of these guys as their nominee.
That would assure a smooth meeting on the 1st. If the SOL did this then Maliki would be out before the meeting and it would end up being a unanimous vote for PM including the SHIA, the Kurds, the Sunni's and the Turkmen.
A unified vote would bring all the sects together for the first time. I believe they will get this done and Maliki will be dumped as the nominee.
Another less combative option and easier way for this to finish is for the SOL to add Chalabi and or Mahdi to the list and then present each one in turn to a vote one at a time.
This would insure Maliki is out on the first vote and that the next on the list would be the PM. I am quite sure Maliki is fighting with the SOL and is against this, but I think this is the plan of the coalition or at the very least it should be.
They are holding back for some reason and I don't think it is infighting in the coalition. If the SOL does not come around and or at least add these two candidates to their list, then at the last minute, or at least when the coalition comes to realize this idea won't work, only then will they announce their own nominee.
If the meeting starts and the SOL only presents Maliki, he will be voted out on the first vote, and the SOL will have isolated themselves with no leader. The coalition will then push forward and finish the process.