I just updated my graph based on two more days of polling figures, and they show that the divergence between the Democrats' and the Republicans' favorables is continuing:

Again, these numbers are "net favorability" for each candidate, meaning, what percentage of those polled have a positive view of them, minus how many have a negative view.
As I surmised on the 15th, these numbers tend to be leading indicators for poll movements, and we are seeing those occur now. I would expect the McCain figures to bounce back; I think most of his hit here is due to his negative campaigning, and if he stops that, he should recover.
But frankly, despite Palin's net favorability now being negative, I think her figures have far more room to drop, at least in the short run. Simply put, more and more people are figuring out every day that she's a dishonest, power-hungry fraud -- and her continued cowardice in avoiding the media almost three weeks after selection makes people nervous about her competence.