One thing that can be said about the Democratic voters in the house, they are fairly rank and file when it comes to votes like this (it was always the senate that was not so all together as far as voting for certain things). If the leadership of the party says vote for someone, they will probably be able to get votes for it so if the establishment wants to help form this coalition, so long as its someone the leadership thinks will do a good job, they can probably get enough to break the tea party voting block with help from establishment wing of the republican party. Of course the big elephant in the room (pun intended) is that any republican who ends up voting in this coalition will likely have a primary challenger on the tea party side to worry about come next year.