It’s been a long, long time since my 8th grade Arizona government class. If Napolitano would leave office, who is next in line for the governorship?
Having said that, I doubt very seriously the Dems would take Janet out of Arizona. She’s much too valuable for them here, for the remainder of her term, and, as you say, a Republican would take her place. She’s done a good job for them in turning a solid red state kind of purplish.
Next in line is Secretary of State, Jan Brewer. AZ does not have a lieutenant governor.