The actual disaster has happened already. Whether Obama and his Democratic Congress can mitigate it remains to be seen.
That seems unlikely if only because democrats were the ones responsible for what has already happened, and some of obama's ideas, like a trillion dollars in new taxes during a near recession wouldn't be advocated by anyone who got a "D" or better in Econ 101.
Whether McCain could have done so no one will ever be able to say.
What McCain would have done is not the issue.