Obviously a sweep is impossible, but I was able to carve out a map with 12 Obama 2008 CDs (pretty sure with a bit more planning, a 13-1 is possible).
After playing around with DRA a bit, I don't think a 13-1 is doable. It doesn't appear to be possible to draw a single district in such a way that the remainder of the state has an Obama plurality. The maximum GOP pack I have been able to draw still gives an 8000 vote margin for McCain in the rest of the state (if you want to make an attempt to prove the theoretical possibility of a 13-1 map though, I recommend you use the "old way" to color by election because the >80% GOP precincts are easy to spot
