McCain campaign manager Rick Davis makes a couple legitimate points in this latest memo, but I'm a little confused as to why Wisconsin would be his baseline for measuring Obama's standing among key demographic groups. (Well, I'm not confused about why he chose it, just why it passes muster.) Davis emphasizes over and over that Obama is down relative to this or that group--Catholics, urban voters, union households--since Wisconsin, but basically unchanged since Ohio. Well, fine. But as Michael Lind explains in great detail here--upper Midwestern states like Wisconsin have a completely different political tradition and sociology than Rust Belt states like Ohio and Pennsylvania. To summarize Lind's argument, they're just a lot more receptive to the kind of progressive, reformist political message Obama has embraced. (I think they're also more progressive racially, but Lind rejects that argument.) Which is to say, Wisconsin to Pennsylvania isn't close to an apples to apples comparison. And when you do make such a comparison--Ohio to Pennsylvania--you don't find much evidence that the last six weeks have really damaged Obama.
Now, obviously, they haven't been great for him either. He certainly didn't make a ton of progress. But there was no problem in Pennsylvania that hadn't already cropped up in Ohio--no new evidence to suggest a "crack" in Obama's coalition, as Davis puts it.