So this applies to OH, FL, VA, NV, and WI but not to CO, NC, IA, or NH (assuming that IA and NH are not in the bag for Obama, which I believe that they are), because there are no Senate races in the latter group.
There is no way that Brown, Nelson, Kaine, and Baldwin (I'm omitting NV there because the polling is all over the place and because Berkley may have her polling numbers understated by the inability of Nevada pollsters to count Latino voters, which we clearly saw in both 2008 and 2010) are winning, most of them comfortably, while Obama is losing or winning by tight margins.
Here's what I mean: MAYYYYYYYBE you can say that since Nelson in FL is no liberal, there are ticket-splitters, but Brown and Baldwin are huge liberals and Kaine is about as liberal as you get for a Virginia senator.
So before you worry about some silly state poll result, look at the Senate race polling. If there's a disconnect, assume the presidential polling is off.
And yes, Gallup is a joke, and a lot of LV models out there are probably going to look pretty silly in about 18 days.