WASHINGTON -- Casino billionaire Sheldon Adelson, who with his wife Miriam spent more than $55 million in an unsuccessful effort to defeat President Barack Obama in 2012, said he would line up behind presumptive Republican nominee Donald Trump in 2016.

"The alternative to Trump being sworn in as the nation's 45th president is frightening," Adelson, chairman of the Las Vegas Sands Corp., wrote in Sunday's Washington Post.

Adelson, who with his wife spent more on the 2012 presidential election than any other donor, said the election of former U.S. Secretary of State Hillary Clinton, the Democratic presidential front-runner, would mean a third Obama term.

"You may not like Trump's style or what he says on Twitter, but this country needs strong executive leadership more today than at almost any point in its history," Adelson wrote. "Trump has created a movement in this country that cannot be denied."

Adelson, a strong supporter of Israeli Prime Minister Benjamin Netanyahu's government, is backing a candidate who once said he had to be viewed as fair to both sides if he was to negotiate a Middle East peace treaty.

"If I go in, I'll say I'm pro-Israel," Trump said during the March GOP debate in Miami. "But I would like to at least have the other side think I'm somewhat neutral as to them, so that we can maybe get a deal done."

He was criticized by both Texas Sen. Ted Cruz and Clinton for appearing to proclaim his neutrality in the conflict.

"I don't think we need a commander in chief who is neutral between the Palestinian terrorists and one of our strongest allies in the world, the nation of Israel," Cruz said during the Miami debate.

Clinton criticized Trump's position in her speech to the American Israel Public Affairs Committee legislative conference in March.

"America can't ever be neutral when it comes to Israel's security or survival," she said. "Some things aren't negotiable. Someone who doesn't understand that has no business being our president."

When Trump addressed AIPAC hours later, he dropped all pretense of neutrality.

"The Palestinians must come to the table knowing that the bond between the United States and Israel is unbreakable," he said. "They must come to the table willing and able to stop the terror being committed on a daily basis against Israel and they must come to the table willing to accept that Israel is a Jewish state and it will forever exist as a Jewish state."

After delegates cheered Trump's anti-Obama comments during his speech, AIPAC's leadership took the stage the following day and delivered a public apology.

Trump was booed during his speech to the Adelson-funded Republican Jewish Coalition in December after he refused to proclaim Jerusalem the undivided capital of Israel. Palestinians seek the Arab section of the city as the capital of their state.

And he was called out by the Anti-Defamation League after he told RJC members that they weren't going to back him "because I don't want your money."

The ADL criticized Trump several other times during the campaign, including his attacks on immigrants, his call to ban Muslims from entering the U.S. and his delay in distancing himself from white supremacists who are backing him.

Trump's earlier comments led some attending the AIPAC conference, including Rabbi Jesse Olitzky of Congregation Beth El in South Orange, to protest his appearance there.

Both Adelson and Trump lined up behind Netanyahu and strongly fought against the agreement to relax economic sanctions on Iran in exchange for curbs on its nuclear program.

Adelson, who called the deal "an issue of paramount importance to me personally" in the Post article, has funded groups and individuals opposed to the agreement, including Rabbi Shmuley Boteach's World Values Network, the Zionist Organization of America and the American Coalition Against Nuclear Iran.

Boteach joined Gov. Chris Christie and others at an August press conference in an unsuccessful effort to convince U.S. Sen. Cory Booker to oppose the nuclear deal. Boteach, who first met Booker at the University of Oxford in England in 1992 and studied Torah with him, has been a critic of the senator ever since.

Trump headlined a Tea Party-led rally at the U.S. Capitol in September in which he said the Iran deal was negotiated by "very, very stupid people."

Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant. Find NJ.com Politics on Facebook