Sheldon Adelson, the billionaire casino magnate, funder of pro-Israeli political extremists, has invited the future potential US presidential candidates from the Republican party for a visit, to see who gets his campaign contributions. This is referred to as Adelson's Republic Primary.
Adelson doesn't do this for fun -- he expects the candidates to march
to his tune, presumably especially on Iran which is a particular concern
of his, which includes his desire to nuke Iran: http://www.theamericanconservative.com/larison/adelsons-deranged-iran-comments/
Specifically, as he explained to an Iranian exile dissident,
"“I really don’t care what happens to Iran. I am for Israel.”
You have to laugh at a system that is so blatantly corrupted that this sort of corruption is deemed "normal".
What's a primary? Its when a party starts the election process to choose candidates that they will run for office. That requires a great deal of money, and so the two parties in the US are keen to cultivate relationships with rich donors like Adelson, who not only can contribute money himself but can also get others to do so too. After all, considering the cost of securing just a senate seat, it is no wonder that elected officials in the US start campaigning for funds as soon as they are elected, since waiting fo election time to roll around would be too late.
This is one step in how candidate vetting is done in the US election process -- through money donations from rich corporations and individuals. The other way is through shaping voting districts so as to minimize competition (and choices for voters) which is why most of the US Congressional seats arent' even genuinely contested in elections. And ironically those election boundary lines are drawn by a committee that consists of representatives of the two parties themselves. This is why the US electoral system is joked about as the only system where the politicians vote for who gets to vote for them. http://www.fairvote.org/research-and-analysis/redistricting/