I am not so sanguine. Just because fewer than all the conservatives left, does not mean that some of the conservatives did not leave.
Why would a liberal vote for Bush yet not vote for McCain? That to me makes little sense. What makes to me more sense, is that some of the conservatives chose not to stick with McCain.
This all goes back to the very origins of the Whig party ~ they were the guys supporting the National Bank! Whenever there were serious financial issues the old Whig wing of the Republican party has been ready to jump ship ~ the morally driven side, the Abolitionists, stayed the course.