No argument. But, it is based on the fact that almost every Schwarzenegger supporter I've heard has said they'd vote for McClintock if he could win. It's not like he is some 3% third party fringer.
I just want to point out that if that is the opinion of 60% of Schwarzenegger supporters, their switch would put McClintock on top, according to the polls.
The silent switch. Just do it on election day.