I should say at the outset that this is a completely moot-point: I am a Republican and Massachusetts has already voted in the primary--so I have no say in the matter.
There are two factors and they work against each other: Of the two Senators, I would rather have Obama as President than Clinton. Obama has a better chance (in my view) of beating McCain than Clinton does. Since I want McCain to win, a Clinton nomination furthers this goal.
If I set values to each outcome and probabilities associated with them, the numbers look like this: Bear in mind, these are just my estimates, which means they are perfect as criteria for setting my opinion.
Value of victory: McCain=80, Obama=30, Clinton=20 NOTE: In reality the McCain # is much less (possibly zero) and the others are negative. The math is easier if all the numbers are kept positive and it doesn't effect the final answer.
Probabilities of victory: McCain v. Clinton = 50:50, McCain v. Obama = 40:60
McCain v. Clinton gives: [(0.5)x(80)]+[(0.5)x(20)]=50
McCain v. Obama gives [(0.4)x(80)]+[(0.6)x(30)]=50
Just in case anybody is suspicious: I didn't choose the numbers to get this result! I did pick nice round numbers because of the uncertainty involved, plus it makes doing the math easy.
It is official and shown mathematically, I don't care who the Democrats nominate!