At the start of the Open, six different women had the chance to leave Flushing Meadows as the new (or current) #1. With the results so far, that race is down to five different players (Kuzzie needed Ana to lose in the first round to have a shot). Thanks to On The Baseline for breaking it down:
A title at Flushing Meadows would automatically give Ivanovic, Jankovic, or Williams the No. 1 ranking.
If Ivanovic reaches the finals and Jankovic does not advance past the semifinals, Ivanovic will remain No.1, regardless of the outcome of the finals.
Current No. 2 Jelena Jankovic and No. 3 Serena Williams must reach at least the semifinals to have a chance at becoming No.1.
Dinara Safina and Elena Dementieva would have a chance at becoming No.1 only if they reach the finals. Dementieva is defending the least amount of points (90 = R16).
Should Safina win the singles title, she would become No.1 if Jankovic does not advance past the semifinals and Ivanovic does not advance past the quarterfinals. (Safina is in the same half of the draw as Ivanovic and Serena Williams.)
If Dementieva wins the singles title and Ivanovic does not advance past the semifinals, she would become No. 1. (Dementieva is in the same half of the draw as Jankovic.)
Of course, there are a lot of other scenarios that would keep Ana at #1. But let's face it people, there will be much bellowing and rending of garments if anyone other than Serena or Dinara leave with the crown. Though if Ana wins the whole tournament, or even just makes the semis, you'd be hard pressed to argue that she hasn't had the best year. But even I know that's not going to happen.