It’s going to be close, but the advertising certainly helps Obama–Clinton’s ads are rather unnoteworthy and Obama has McCaskill in them as well as Lacy Clay and the Carnahans supporting him and apparently working pretty hard for him.
Survey USA doesn’t show any closing, but the others show it as a virtual tie and that’s what I’ve been hearing for a week from different campaigns–including statewide campaigns not involved. Again, Survey USA seems to show a lower African-American turnout than I expect by 4-5 points so I think Obama will take a slight win.