Daniel Levy speculates:
If a ceasefire is becoming imminent, then it is fair to assume that while the dynamics of the conflict (Israeli recoil from fully re-occupying Gaza), and the diplomatic effort have played a role, the key element to timing here is the approaching Obama presidency.
Increasingly, I think this entire operation is about Obama. The Israelis are showing that they know the incoming president is a grown-up and will likely force them to come to some difficult but vital decisions about their future. So they're increasing their leverage as best they can - largely by launching an operation that is both legitimately designed to weaken Hamas as much as possible and illegitimately designed to punish Palestinian civilians for voting for the wrong leaders. Levy continues:
First of all, the various actors--and one imagines Israel in particular--will not want to piss on Obama's parade this Tuesday. More substantively, there is an expectation that the new president would have felt compelled to immediately intervene in this situation. While there is an assumption that the Obama administration will remain strongly supportive of Israel, one can also anticipate a more thoughtful articulation of what serves American interests in the Middle East, how the close Israel-America relationship should be managed, and the taking of corresponding efforts to immediately de-escalate this spiraling crisis. It might be pushing the envelope to call Obama the peacemaker here, but it's hard to deny that his impending entrance to the world stage has an effect.
If this conflict does now end (as one desperately hopes it will), then it will of course be the Obama administration that is left to deal with the fall out. The memo of understanding, due to be signed by Israel and the US tomorrow, is one part of that. It seems to be a smart move by Condoleezza Rice to give this to the Israeli Foreign Minister in order to get her fully on board for ending the war. If it is indeed mostly political theater, an election campaign photo-op for Livni, then so be it. But if it amounts to more, then this might well be one final poison chalice that the Bushies are bequeathing to 44. If America is to play an active military role in the Sinai, then expect complications and a scenario with all the makings of nurturing over time another insurgency with possible blowback, and even with consequences for the shaky and unpopular regime of Egyptian President Hosni Mubarak.