I'd say one of the good way to predict whether a county will flip is use Google maps from 2008/2012 and see what kind of construction is being done in the suburb counties(how dense). Hays most of the new subdivisions in Hays county seem to be pretty dense(near Austin), and there are a couple new apartment complexes I found in San Marcos. There is a big subdivision west of San Marcos that looks like a country club that grew a lot however.
What about Deschutes county in Oregon or Spokane county in Washington? Those were nail bitters in 2008.
Deschutes will almost certainly go Obama, Spokane will likely go Obama.