The popular incumbent would be the favorite. Incumbent Governors can survive midterms that suck for their party.
That's the thing -- will it be a CA/CT/HI/MN '06 / AR '10 (popular incumbent Governor in a state that doesn't favor their party survives in a midterm that sucks for their party) or a MD '06 (popular incumbent Governor in a state that doesn't favor their party goes down with the wave)? I think it could really go either way, but gun to my head, I'd have to lean toward MD '06 since being the same state makes the parallel stronger.