Absolutely. If Kelley gets to the end she would be hard to beat IMO. But I'm with Oscirus in thinking that while Spencer is a more visible and overt player, he might look more like a cog in an "alliance" that was perceived to be lead by Jeremy - if that makes sense. Though if Spencer makes it to final 3, he is capable of making a case for himself. For Jeremy, on the other hand, if he does make it to Final 3, as you said, can he make the argument that he played the best game? I don't know.
For any of these three, I think they'd be thrilled to go to the end with any combination of Abi, Kimmi