Because the Dark Lord would become President, and I'll be honest...that scares me more than 18 more months of Shrub.

Voldemort vs. Cheney

That's an MTV Celebrity Death Match that I'd have to say would be too even to call before the match began.

Can you just imagine life under President Cheney?
Scenario 1: Within three weeks of assuming power, he declares that Iran is actively participating in the insurgency in Iraq and launches bombing attacks on Iran. Within 3 months, "the nuclear option" will discussed weekly on the national news.

Scenario 2: It is revealed that Cheney's war profits from his retained stocks in Halliburton and its progeny exceed the annual budget to run Congress. He resigns in disgrace and Nancy Pelosi becomes the first female POTUS. In order to appear tough, she almost makes the same mistake Cheney makes in scenario #1.

Scenario #3: Minutes after inauguration, Cheney's skin splits and peels back, revealing him to be a Dalek who assumes complete control of the earth until an odd little man known only as Dr. Who suddenly appears and restores order.
(you have to know the BBC for this one to make sense.)

Not a pretty picture any way you look at it.