Exactly.
Osama knows that Bush has been relentless is attacking the Islamist movement.
Osama has no clue as to how Kerry will react, honestly, I doubt anyone does, including Kerry himself.
Looking at that logically, it is obvious that for Osama, Kerry would be the one he would prefer.
A Democratic president would never be constrained in foreign policy the way a Republican president is. Do you think Michael Moore would ever make an anti-Kerry movie under any circumstances -- even if Kerry's approach to the "war on terror" involved large-scale attacks on Islamic nations that resulted in the death of a billion Muslims?
The dirty little secret in this country is that we turn to Democrats whenever we feel a need to pursue things that we would never allow a Republican to do -- whether it be the internment of Japanese-Americans in World War II, the assassination (or assassination attempts) of foreign heads of state in the early 1960s, the Vietnam War, welfare reform and "tax cuts for the rich" in the 1990s, etc.
Osama bin Laden probably knows this as well as anyone.