WASHINGTON/BEIRUT, Dec 1 (Reuters) - U.S. President-elect Donald Trump on Sunday said Lebanese American businessman Massad Boulos would serve as senior adviser on Arab and Middle Eastern affairs.

Trump made the announcement on Truth Social. Boulos, the father-in-law of Trump's daughter Tiffany, met repeatedly with Arab American and Muslim leaders during the election campaign.

It was the second time in recent days that Trump chose the father-in-law of one of his children to serve in his administration.

On Saturday, Trump said that he had picked his son-in-law Jared Kushner's father, real estate mogul Charles Kushner, to serve as U.S. ambassador to France.

In recent months, Boulos campaigned for Trump to drum up Lebanese and Arab American support, even as the U.S.-backed Israel's military campaign against Hezbollah in Lebanon.

Boulos has powerful roots in both countries.

His father and grandfather were both figures in Lebanese politics and his father-in-law was a key funder of the Free Patriotic Movement, a Christian party aligned with Hezbollah.

His son Michael and Tiffany Trump were married in an elaborate ceremony at Trump's Florida Mar-a-Lago Club in November 2022, after getting engaged in the White House Rose Garden during Trump's first term.

Boulos has been in touch with interlocutors across Lebanon's multipolar political world, three sources who spoke to him in recent months say, a rare feat in Lebanon, where decades-old rivalries between factions run deep.

Particularly notable is his ability to maintain relations with Hezbollah, they say. The Iranian-backed Shi'ite Muslim party has a large number of seats in Lebanon's parliament and ministers in the government.

Boulos is a friend of Suleiman Frangieh, a Christian ally of Hezbollah and its candidate for Lebanon's presidency. He is also in touch with the Lebanese Forces Party, a vehemently anti-Hezbollah Christian faction, the sources say, and has ties to independent lawmakers.

Aron Lund, fellow at the Century Foundation think tank, said Boulos was well placed to influence Trump's Middle East policy after playing a small but significant role in expanding Trump's appeal to Arab American and Muslim voters during the campaign.

"Boulos' Lebanese political past gives no real indication of a geostrategic or even national vision, but it demonstrates ambition and a set of political allies that will stand out in Trump's circle like a sore thumb," Lund wrote.

MICHIGAN WIN

Boulos, a billionaire with extensive business ties in Nigeria, was born in Lebanon, but moved to Texas as a teenager, where he attended the University of Houston, earned a law degree and became a U.S. citizen.

His son and Trump's daughter, whose mother is Trump's second wife Marla Maples, met on the Greek island of Mykonos, at actor Lindsay Lohan's club, People Magazine reported in 2022.

Trump's election win in Michigan came in part because of Boulos' help flipping some of the 300,000 Arab Americans and Muslims in the state who overwhelmingly supported Biden in 2020 but opposed Biden's policies in Israel, Gaza and Lebanon, Trump campaign officials and supporters told Reuters.

"Boulos played a big role in the outreach to Muslim voters," said Rabiul Chowdhury, co-founder of Muslims for Trump.

Beginning in September, the Trump campaign held weekly meetings in person and via Zoom with dozens of Arab American and Muslim civic leaders and business executives.

Boulos spent weeks on the ground in Michigan, Pennsylvania and other states with big Arab American and Muslim populations, assuring audiences in private lunches and dinners that tapped his own connections to Lebanese American businessmen that Trump was committed to ending the wars in the Middle East.

The Trump campaign spent tens of millions of dollars on the effort to mobilize Arab American and Muslim voters, Boulos told Reuters in an interview shortly after the election.

Trump won endorsements from Muslim imams and the Muslim mayor of Hamtramck, another town near Detroit with a large Arab American population, as well as the large Bangladeshi community, and courted Iraqi Americans, Albanian Americans and others.

While the events on the ground in Lebanon played a factor, the economy did too. And conservative Arabs and Muslims were concerned about what they saw as the Democrats' "far left ideology," including support of transgender rights, Boulos said.

Boulos met with members of the 150,000 strong Albanian community in Michigan.

POLITICAL AMBITIONS?

The new role could offer Boulos the kind of political clout he could not achieve in Lebanon. He had a brief run for Lebanon's parliament in 2018 alongside pro-Hezbollah candidates, but since then he has not consistently aligned himself with any particular party, sources in Lebanon said.He hails from a Greek Orthodox family. In Lebanon's sectarian powersharing system, that would cap his chances at a senior role in government at the level of deputy speaker of parliament. The post of president - the highest Christian role in the country - is reserved for Maronite Catholics.

While he used to travel to Lebanon frequently, he has not visited in the last four years, one of the sources said.

Some people in Lebanon were hopeful about the prospects of having a friendly face in Trump's inner circle even before the announcement on Sunday.

"It's a nice thing - and hopefully he will work for Lebanon. And Trump maybe is of the type who makes a promise and could possibly be more loyal to it than others," said Hamdi Hawallah, a Lebanese man in his late 70s.

"So we're optimistic about him. These days we hold on to a piece of driftwood just to be optimistic."

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Reporting by Andrea Shalal in Washington and Maya Gebeily in Beirut, additional reporting by David Ljunggren; Editing by Heather Timmons and Alistair Bell