Of course Obama is a factor. But, you have to remember that McCain has had problems on the right, and my friends are still smarting from a number of McCain stunts.
As I am. Still, there is no way I would vote for the cooked-up candidate, Barry Soetoro, aka “Barak Obama”.
Many conservatives would like to fire as powerful a shot as possible across the bow of McCain and the GOP without sinking them. If conservatives can get fired up about trying to boost Barr's numbers in states like Illinois or Alaska where their vote can't possibly tip the presidential race(*) and will thus make sure they get to the polls and VOTE for the other offices, that would seem better than having them apathetically maybe vote for McCain or maybe not bother (thus not voting for other offices either).
(*)If McCain would be within a vote of winning Illinois or losing Alaska, the election elsewhere is going to be sufficiently lopsided that Illinois' and Alaska's votes aren't going to matter.