Surprised to see people saying Mueller. I personally am not much of a fan of hers (as I've said many times before on this board), but the Tonys seem to love her, and it's a very meaty role. I definitely wouldn't have guessed her as one of the bottom 2.
I figure it had to be some combination of Kilgore, LaChanze, and Louderman. My guess would be Louderman and LaChanze. I know lots of people love Louderman's performance - I'm not of that camp, so maybe I'm biased. But I also think hers is the least "leading" of the 6, and also requires the least acting. I haven't seen LaChanze's performance, but I'd guess her because the show was largely ignored, so it makes sense that she would have just barely gotten in.