Bad analogy. Dubya isn't running for anything in 2008. But we can send the message that if the GOP doesn't listen to the base regharding immigration, we will stay home.
I didn't say he was, but a Republican will be running for President. I suggested we threaten him (GOP, same thing, we all know GWB isn't running) with voting dem, you suggest we threaten him with staying home. I doubt that's going to be effective. The time for that message in in 2006 and 2008, and in the primaries.