SecDef Panetta is trustworthy from the Israeli perspective. He is former director of the CIA, and has intricate knowledge of US-Israel defense cooperation. While diplomatically the US and Israel have had differences over the past three years, US-Israeli defense cooperation has only increased. Sending SecDef Panetta is a good way for the administration to exploit its strengths vis-a-vis the Israeli government. In an election year, this objective has heightened importance.
At the same time, the changing of the guard at the Pentagon allows Panetta a chance to introduce policy modifications. While heading the department with the closest alignment with Israel, Panetta called for Israel to "try to develop better relationships" with its neighboring countries, a rather explicit recommendation which may very well have been condemned had it come from the White House.
But there is another important message the Obama administration is sending with Panetta's trip. By sending SecDef Panetta this diplomatic round, the US has created a strong incentive for Israel not to alienate their American point of contact. The SecDef has extensive executive authority and is low enough in the chain of command that his message can be slightly less politically sterile than the President. While embarrassing Vice President Biden was a diplomatic fiasco in and of itself, alienating the American Secretary of Defense would be far more risky for Israel. Not only would there be a risk that physical aid to Israel might be jeopardized, but also the political cost in Israel would be higher. Israelis may have their disagreements with the Obama administration, but they also understand the US-Israel relationship to be of high strategic importance.
SecDef Panetta's offers the Israeli government an opportunity to strengthen the core of its relationship with the United States. However, it carries with it the risk of alienating one of the US government's most important principals from the Israeli perspective. In this regard, Secretary Panetta's visit is both a carrot and a stick.