He suggests they have a roughly 17 month window of opportunity to attack Israel. If current trends continue, 17 months from now a Republican president will be inaugurated who will defend Israel essentially without limit. At that point, for Israel's enemies the "window of opportunity" slams closed.
The most strategic time to strike Israel would be between the November, 2012, election and the January, 2013, inauguration. A lame duck president, whose basic inclination is to side with Muslims, has little to lose by dithering, leaving the problem for his successor.