Pretty much all the elected leaders above a certain level seem to need to make their pilgrimage and kiss the ring.  Pictures exist of all recent presidents doing the same thing, and I cannot think of a one who didn't go to Israel and do undefined 'things' before they 'won' their primaries.  Obama is a classic example of this.

It doesn't strictly speaking 'prove' anything, but it makes a hell of a strong statement about who runs the U.S..  What other country and religion to presidents act like this toward?  Jews make up about 2% of the public.  That's a lot of hassle (not to mention humiliation) for not a whole lot of votes, eh?