Neither of them take Chomsky seriously, who said in the beginning that were democracy ever actually our goal in Iraq, a split-up would be almost certain. However, he also warned state planners would never let that happen.
I presume the Bush PR team will want to put into place some kind of formal democracy, as long as it has no substance. But it's hard to imagine that they would allow a real voice to the Shi'ite majority, which is likely to join the rest of the region in trying to establish closer relations with Iran, the last thing the Bushites want. Or that they would allow a real voice to the next largest component of the population, the Kurds, who are likely to seek some kind of autonomy within a federal structure that would be anathema to Turkey, a major base for US power in the region.
There are also risks, which Biden acknowledges, in such an approach. The central government might be too weak to fend off external threats. Regional autonomy could lead to permanent division of the country.
There's no "could" about it, but since we'll never outright declare that Iraq must become three separate nations permanently, this is likely the only way we're able to let the inevitable manifest itself (and is unlikely to happen at all if Bush is allowed to keep steering this war). Then we can say "Oops, we didn't mean for that to happen! If those Shias get too chummy with Iran we'll have to take measures!"
I'm glad that some Democrats and establishment types, always thinking in molasses but quicker than in Vietnam, are finally moving towards recognizing what's going on in Iraq. And I'm disgusted that those who have been right all this time have to listen to these Neo-Columbuses hooting about how they just discovered America.