I hate to say it, but this is a really smart move by Obama.
By all accounts the GOP right now is fractured. Obama wants to drive a wedge in that fracture, and immigration might do it.
However, this might backfire in an epic way on Obama. If the GOP in the House hold firm together then this bill will either die, or come out in a much more GOP friendly way.
The reason the GOP fractured over the debt limit was the doomsday ideas being put out there, they are debatable, but enough bought into it.
There is no such doomsday if the GOP doesnt pass Amnesty, its really the opposite actually. Starve the Democrats of those voters.