I would think PA would be more winnable than MI for a number of reasons (auto bailout, fracking/coal, slightly more Catholics, higher Appalachian hating of Obama than in 08), but I suppose they have polling and possibly focus groups that say otherwise.
You know, when you need states on your secondary list to win, it's not a secondary list.
The "primary" list is the states that they think Romney must win, and the "secondary" list is the states that Romney only needs one of as long as he sweeps the primary list.