As a baby boomer born in the early 1950s, I learned the concept of Jewish peoplehood early on: not only did I grow up to be a proud American with an unwavering loyalty to my country, but also to be a proud Zionist devoted to the State of Israel. These concepts were instilled in me by my parents – my father whose parents were immigrants from Eastern Europe and my mother whose family arrived in America in the 1800s.These two identities have never been in conflict for me, and my commitment to both has been the cornerstone of my life, giving me an excellent vantage point from which to observe the Jewish communities in both the US and Israel.I have traveled to Israel more than 50 times on family, business, philanthropic and political missions, have close family and friends there across the political spectrum, from far Left to far Right, and have met with every prime minister since Golda Meir. My businesses over the past 25 years – in retail, manufacturing, construction and real estate – have me working with both Israelis and Palestinians.If there is one lesson I have learned it is that if you want an Israeli to do something, you need patience, tact and a willingness to work to instill confidence and trust. You can’t walk in and say, “Do this.” That is among the reasons I fear a Donald Trump presidency. Simply put, his style and temperament, coupled with his thin skin, inconsistency and woeful ignorance of foreign policy, are incompatible with good relations with Israel – and Israelis.Israelis need to know that an American president has their back. Trump has already said that allies should pay back the military assistance the US gives them, and that includes Israel.“I think Israel would do that also,” he said several months ago. “There are many countries that can pay, and they can pay big-league.” Though he recently walked back that statement, saying that Israel is what he calls a good “investment,” it’s difficult to know when he’ll flip again – or what happens when he somehow calculates that it no longer is a good investment.Through his inconsistent statements about foreign policy, Trump has displayed frightening ignorance.He has pledged time and again to rip up treaties and agreements and, among other things, has criticized NATO as being “obsolete” and has said, “We can’t defend Japan.” Such decisions would be disastrous for America’s relationships and could leave Israel in a vulnerable position.It’s not hard to imagine Trump one day saying he would rip up accords with Israel as well.A Trump presidency would jeopardize US strength and reliability, and would hurt Israel. The Republican platform for the first time says nothing about a two-state solution, which has been central to our nation’s Middle East policy for decades, and a Trump adviser has said that the candidate does not support a two-state solution.Apparently, Trump and his top advisers would prefer to see Israel annex the West Bank and east Jerusalem.Does he recognize that were it to do so, Israel within just a few short years would lose its Jewish identity and majority? His tendency to portray Muslims in broad strokes, often giving the impression that he assumes all Muslims are terrorists unless proven otherwise, feeds into anti-American sentiments in the Arab and Muslim world and would make it more difficult for the US to help Israel in its quest for peace.Trump’s authoritarian tendencies will get him nowhere with Israelis, who will resent such heavy-handed interference from a country they want as a strategic partner but also as a friend.In “For All These Things,” Naomi Shemer sings, “Every bee that brings the honey needs a sting to be complete/ And we all must learn to taste the bitter with the sweet.”Yes, Israelis will have to make bitter compromises for a sweet peace, but Trump will not be able to coax either Israelis or Palestinians to make compromises, for he has such a sting, but his bombastic temperament contains no honey.The author is the treasurer of Jews for Progress, a pro-Hillary Clinton super PAC, and a member of the Conference of Presidents of Major American Jewish Organizations.