Mr Netanyahu spent most of his early life in the United States and, throughout his entire diplomatic and political career, he has had close ties with the American political establishment. He knows its rules and patterns, but the Trump phenomenon is as baffling for him as it is for just about every other veteran observer of the American scene.
He has tried, until now, to keep his distance but, as of last week, he is in danger of being sucked in.
Last Friday, Sheldon Adelson, the Las Vegas billionaire and Mr Netanyahu's most prominent American supporter, wrote an op-ed for the Washington Post, endorsing Mr Trump. Citing the candidate's executive experience and the need to ensure that the next occupant of the Oval Office is a Republican, Mr Adelson called upon his fellow party members to fall in behind the Donald.
Not every Republican can get one of the most important newspapers in the US to run his own personal endorsement on their editorial page, but Mr Adelson is not just another political donor.
The 82-year-old who made a small fortune from IT trade-shows and then his billions from mega-casinos and resorts, is often, mistakenly, called the "richest Jew in the world" and the biggest mega-donor in American politics.
Neither title is accurate. The Koch brothers on the right and financier George Soros on the left have given more money over the years to political causes and candidates.
On the latest Forbes billionaires list, Facebook founder Mark Zuckerberg, Oracle's Larry Ellison, Michael Bloomberg and the Google duo Larry Page and Sergey Brin all feature above Mr Adelson. But with an estimated personal fortune of $25.2 billion, at 22 on the list (one spot above Mr Soros), he remains one of the richest men in the world and is certainly the one who makes the most flamboyant and unabashed use of his wealth to promote his favoured politicians.
While other tycoons prefer to keep their donations and involvement in politics low-key and behind the scenes, Mr Adelson revels in his influence, holding open events with Republican candidates that, more than anything else, resemble auditions.
In the race for the nomination in 2012, it was largely Mr Adelson's money that kept the former speaker Newt Gingrich in the race for many months, causing, some said, damage to the eventual candidate, Mitt Romney. This time, Mr Adelson kept his powder dry for most of the primary season, though he was widely rumoured to favour the young senator Marco Rubio.
Now that Mr Trump is the only man still standing and, by default, the presumptive candidate, Mr Adelson has finally shown his hand, calling on the many wavering Republicans - some of whom are even considering a vote for Hillary Clinton - not to break ranks. His endorsement has wider implications far beyond the US, however.
The origins of the Netanyahu-Adelson friendship are obscure, but they go back a long way. In 1991, the then deputy foreign minister helped organise Mr Adelson's second marriage in the Knesset foyer.
At that time a little known businessman, Mr Adelson was to come to prominence on the Israeli political scene over a decade later when he was named as a potential buyer for daily newspaper Maariv.
Then, in 2007, Mr Adelson founded Yisrael Hayom, a newspaper which is distributed freely throughout Israel. Unlike other freesheets available on metropolitan public transport systems, Yisrael Hayom is a full-scale editorial operation, employing hundreds of journalists and available at street-corners and coffee-shops nationwide. And unlike the standard freesheet that exists only to make money from advertising, Yisrael Hayom is funded privately by Mr Adelson, at a rumoured $50 million a year and has no incentive to turn a profit.
Its sole justification is to support Mr Netanyahu and his policies, exploiting what is effectively a loophole in Israel's relatively strict political finance laws which severely limit the sums individuals are allowed to donate to parties and candidates, and forbid corporate donations.
Mr Adelson has also donated hundreds of millions of dollars to programmes such as Birthright-Taglit and to institutions including the Yad Vashem Holocaust memorial in Jerusalem, to which he is now the largest single donor. Such generosity has cemented his position as one of the most influential figures in the Jewish world.
A staunch opponent of the nuclear deal with Iran, any Israeli retreat from the West Bank and the establishment of a Palestinian state, Mr Adelson has made it clear that his willingness to donate to a particular political campaign is connected directly to the candidate's level of support for Israel.
At first, the two casino owners, Adelson and Trump, did not seem natural political bedfellows. While proclaiming his love and support for Israel, Mr Trump has worried the decision-makers in Jerusalem with his statements that he would be "neutral" on the Israel-Palestine conflict and that countries that receive American aid (of which Israel is the largest recipient) should start "paying back".
Throughout his bid for the nomination, Mr Trump also boasted - not entirely truthfully - about how he has funded his own campaign and that, unlike other candidates, he is not beholden to Republican donors. But in recent months, as the once unthinkable prospect of a Trump candidacy began transforming into inevitability, the pair drew closer.
Mr Trump may have enough money for the primaries but the general presidential election in the United States is a billion-dollar affair and he certainly has no plans to spend that kind of money from his own bank account. He needs the Republican mega-donors now, especially given that at least some of them are much more reluctant than usual. He also needs the imprimatur of well-known figures like Mr Adelson to overcome the Republican establishment's hostility towards him.
One interesting signal of the growing affinity between Mr Trump and Mr Adelson in recent months has been the editorial line of Yisrael Hayom, which, while not intended for American primary voters, has served as a reliable barometer of the thinking both in Mr Netanyahu's inner circle and in Mr Adelson's Las Vegas office. In the early stages of the Republican race, it was fairly neutral. As the primaries began it seemed warmer towards Senator Rubio, and then his rival, Senator Ted Cruz. But in the past few months, it has clearly shifted towards the Trump camp, running no less than three interviews with him, a record for any non-American news organisation.
The question remains, however, how far all this will affect Mr Netanyahu.
In 2012, he hoped and believed that Mr Romney was about to turf President Obama, with whom he has a rancourous relationship, from the White House. While officially remaining neutral, Mr Romney's reception in Jerusalem was effusive and included both a meeting in his office and a private dinner at the prime minister's residence.
This time around, Mr Netanyahu is expected to be more cautious. With nearly all the polls favouring the assumed Democratic candidate Hillary Clinton, he certainly does not want to be seen to be as endorsing her rival. But Mr Adelson's endorsement could make that a lot more difficult. In recent weeks, Mr Trump has said that his visit to Jerusalem, before the elections, is once more on the schedule. And the Donald will not make do with just a photo-opportunity.
