President-elect Donald Trump speaks during a rally at Ladd-Peebles Stadium...

President-elect Donald Trump speaks during a rally at Ladd-Peebles Stadium in Mobile, Ala., Saturday, Dec. 17, 2016. Credit: AP

Two vastly different Long Island enclaves have snared the attention of President-elect Donald Trump during the transition.

On the evening of Dec. 3, his motorcade rolled up to a Head of the Harbor mansion for a lavish costume party. Trump emerged wearing a suit, signaling to a reporter he was dressed as himself. Aide Kellyanne Conway arrived as Superwoman at the “heroes and villains”-themed fete.

Hedge-fund heavyweight and top political donor Robert Mercer played host. He and his daughter, Rebekah Mercer, gave millions of dollars and key advice to Trump’s campaign effort. The family manse overlooking Long Island Sound includes a $2.7 million model train set and a machine gun collection, according to a Newsday profile.

Mercer is co-CEO of Renaissance Technologies, based in East Setauket, which represents more than just another big investment enterprise.

The firm retains a cutting edge in high-finance circles.

Last month Bloomberg Markets described Renaissance’s Medallion Fund as “shrouded in secrecy and fueled by a combination of science and finance.” It reportedly “produced around $55 billion in profit for the company’s employees over the past 28 years.”

“Perhaps the world’s greatest moneymaking machine . . . Medallion is open only to Renaissance’s roughly 300 employees, about 90 of whom are Ph.D.s, as well as a select few individuals with deep-rooted connections to the firm.”

Some neighbors even call a cluster of mansions near the company’s 50-acre corporate campus the “Renaissance Riviera.”

Eleven miles to the south is Brentwood — a world away from glitz and global investments.

In the 1850s it was the site of a utopian community called Modern Times. Today, Brentwood is majority Hispanic, with many from El Salvador. The hamlet has a median family income of $57,047, according to the most recent census.

Brentwood has attracted Trump’s notice from his lofty perch 45 miles away. Speaking to a Time magazine reporter in the dining room of his Trump Tower apartment, he stopped the interview and said, “Let me go upstairs for one second and get you a newspaper article.” He returned with Newsday from Nov. 28. The front-page story tied an extremely violent faction of the MS-13 street gang, which hails from Central America, to as many as six recent killings in the area.

Since 2002, prosecutors working with the Long Island Gang Task Force have won convictions of several hundred MS-13 members on Long Island.

“They’re tougher than any people you’ve ever met,” Trump told Time. “They’re killing and raping everybody out there. They’re illegal.”

With the accustomed braggadocio, Trump added, “They are finished.”

Trump, meanwhile, tapped deep-rooted Long Islanders for federal posts.

David Friedman, son of the late prominent Woodmere rabbi Morris S. Friedman, is the choice for ambassador to Israel. Friedman was Trump’s bankruptcy lawyer. Also, Kathleen “KT” McFarland, a longtime Southampton resident, will be deputy national security adviser.

Political Long Islanders have made their way through the gilded lobby and offices of Trump Tower as well.

Last week, Rep. Peter King (R-Seaford) and his daughter, Hempstead Town Councilwoman Erin King Sweeney, joined with Suffolk Republican Chairman John Jay LaValle in a 45-minute meeting with the president-elect.

The closed-door meeting was said to have focused on national security.

Take from the recent encounters that Trump, who won more votes in Nassau and Suffolk combined than Hillary Clinton, remains no stranger to the Island.

What that might mean locally — and to which of its residents — remains to be seen.

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