Allow me to guess at the particulars:
Israel fears fecklessness in the US Executive if Obama is elected.I didn't realize, until Rush mentioned it, that apparently the candidates had received some sort of national security briefing recently, and so maybe Joe let slip something he knows is likely but has, at least to this point, the sense not to state with specificity.
Israel mortally fears the consequence of an Iranian nuclear weapon coupled with the above.
Israel does what it thinks it must to secure its survival and takes out Iranian nuclear assets.
Obama responds by condemning Israeli aggression.
Of course, as an electoral matter, this should be viewed as a classic Kinsley gaffe, defined as when a politician accidentally speaks the truth. This admission against interest by Biden, though, will have the same curious "tree falls in a forest" non-effect that so much else of the Obama campaign has had. With no MSM outlets caring much to question things that would seem obvious (conflicting reports regarding place of birth and a questionable birth certificate, transcripts from his two colleges and Harvard law school, activities as a community organizer and ACORN buddy, New Party endorsement, waste of tens of millions of dollars in pursuit of indoctrination of elementary school students at the expense of education, socialist economic doctrine, etc), will Biden's prediction even be made known to a significant portion of the electorate?