That 527 attack ad against Obama which links him to Bill Ayers and 9/11 is reprehensible and so over the top it's almost hard to take seriously. But it's clearly deadly serious. Josh Marshall's readers report seeing it constantly in Ohio. And now the Obama campaign has come up with a somewhat defensive response ad of its own.

Unfortunately, fights like this on the airwaves may be nearly as important as what happens here in Denver.

--Michael Crowley