I doubt the professional politicians who are making big decisions actually have such wildly disparate predictions. Rather it seems that political amateurs have lousy predictions about who is likely to win--not surprising since the stakes for amateurs are pretty low. Intrade has Obama's chances at 51% for reelection. I would be surprised if the GOP leaders in Washington are banking on winning the trifecta.
*Edited to fix a typo (of should have been if -- in the last sentence).
What makes you think the professional politicians are any better than say, Nate Silver or the pollsters, all of whom go into the Intrade stew? Politicians routinely make epic mistakes ranging from their personal life to grand strategy (in fact, one such example - Newt Gingrich and the government shutdown - has multiple parallels in modern American politics, from Gingrich himself being back to the recent near government shutdown).
Related to: Politics is the Mind-Killer
Both sides seem to have a stake in the current budget supercommittee failing. Why?
The NYTimes reports:
In other words, the Republicans believe they can achieve complete victory so that they can enact their whole agenda, while Democrats believe they can block this victory.
On a key component — Obama's re-election — Republicans believe they will defeat Obama with 1:6 odds, while Democrats believe this event has only 3:2 odds.**
With a 9-fold difference in this key perception, it seems highly unlikely the two will reach a compromise.
* Not necessarily true — you can't just multiply 74%*72%*83% as these events have high positive correlations.
** Yes, perhaps the people in power have different perceptions than the rank-and-file electorate — but they still must win their base's support to gain re-election.