The McCain campaign has allowed Sarah Palin to do what she does best. In the final stretch of the campaign, the overriding narrative of the attacks on Obama are going to paint him as unsafe. Linking him with Bill Ayers and Jeremiah Wright.
This is not something that is very different to what you get in a normal presidential campaign. The vicious and spurious kind attack politics was going on even since Jefferson and Adams.
If those two succumbed to that kind of campaigning then it's hard to make too much of a big deal about McCain.
However let's not underestimate the damage this does to the nation.
Negative attacks aren't bad just because they are mean. No one cares about being mean to a politician. Negative attacks are a problem because it interferes with governing.
Obama could go all out and attack McCain on his associations with dubious figures like Pastor Hagee. He could attack him on McCain's treatment of his ex-wife. Those kinds of attacks work because the press will cover them extensively. They are more entertaining and easier to follow than policy debates.
But Obama will also alienate a lot of pissed off republicans. When it comes time to govern, that's going to impede his bipartisan efforts. And let's face it, we need compromise and bipartisanship if anything is going to get done.