Oh, Horse crap!
I know math.
According to your statement above: no, you don't. A null vote is not the same as a vote *for* Obama. it is null. It has no potential.
And anyway, why stay home when there is a Conservative choice (and pssst! that ain't Romney)?
Sorry my FRiend but you are wrong. In a two part balancing equation, failure to add to one side (not voting) increases the imbalance between the two sides. It is the same as adding one to the other side.