Israel has become a must-stop on the campaign trail in the Republican Party's primaries for the presidential nomination in 2016.

Eager to burnish their foreign policy credentials and to appeal to the influential Jewish GOP donors, they pray at the Kotel and go on helicopter rides to see Israel's slender borders. Unofficially, it is being called "the Adelson audition".

Last week, it was Senator Lindsey Graham making the visit, which naturally includes a photo opportunity with Prime Minister Benjamin Netanyahu. Three weeks ago, Wisconsin Governor Scott Walker did the rounds.

Key Republican donors include former New York mayor Michael Bloomberg, and Larry Mizel, the chairman of the Simon Wiesenthal Centre. But above all, the candidates have in their sights casino tycoon and Netanyahu supporter Sheldon Adelson, who reportedly spent over $100 million on the presidential campaign in 2012.

Another candidate expected in Israel is Senator Ted Cruz, who is scheduled to arrive next month on his third visit in a year and a half. The candidate rumoured to be closest to receiving Mr Adelson's backing is Florida Senator Marco Rubio. Mr Rubio visited Israel in 2012, and is expected at Ben Gurion again soon.