Kuchma is likely to respond with one last round of negotiating with the Rada. He has already put down a marker by vetoing a bill that would have stopped absentee ballots, which many feel are the chief means by which vote fraud occurred in the last round. This isn't necessarily a final decision, since the parliament and Kuchma will have to hammer out procedures for the runoff election its Supreme Court has ordered.

The other lever available to Kuchma is the fourth point in the agreement signed between him, Yushchenko, Yanukovuch and European observers on Wednesday:

Sides also agreed to admit political reform on the basis of Law-project No.4180; this should be done together with changes to Law about presidential elections as well as with forming of new Cabinet of Ministers.

Law 4180 is important -- it changes the appointment of the prime minister from the presidency to the parliament and invests the office with greater power than it had before, most of it taken from those currently held by the president. In short, it has the potential to make the position Yushchenko has fought so hard to acquire mostly ceremonial. This bargaining position is probably the last foxhole Kuchma has. His signature on the agreement should by law also end his term as president (it officially expired Wednesday). So it is most likely he will hold on for dear life to get the best possible outcome. James Sherr anticipated this yesterday; the possibility remains open that Kuchma himself could be made prime minister (an outcome Sherr doubts -- I am not as sure.) He adds (emphasis mine):

The determination of Ukraine�s authorities to remain in power overrides any need to be honest with honest brokers. To these authorities 'compromise' is a means of struggle. Given this fact, there could be adverse consequences in Ukraine if the EU pursues it as an end in itself. For Ukrainians, the issue is legitimacy, not stability.

The parliament has agreed to stay in session through the weekend. No doubt they'll need it. Will the EU have the courage to see this through?

UPDATE: I forgot to mention this: Part of the evidence of Kuchma's wrangling here is that there is talk that Yanukovych will withdraw from the repeat 2nd round. If he did the runoff would be against the third place finisher Oleksandr Moroz (he received 6% in the first round on Oct. 31.) But if he waits until Dec. 6th, then Yushchenko would run against "none of the above" and needs 50% to win. Unian also reports (article in Ukrainian currently) that there is expectation that if Moroz were to enter the race for Yanukovych, a deal would be struck to have him withdraw as well, perhaps to become PM instead (if Yushchenko had the power to make the appointment still.)