WASHINGTON — Relationships have always been President Trump’s currency and comfort, helping him talk his way into real estate deals over three decades in New York. Those who know him best say that his outer confidence has always belied an inner uncertainty, and that he needs to test ideas with a wide range of people.

As Mr. Trump’s White House advisers jostle for position, the president has turned to another group of advisers — from family, real estate, media, finance and politics, and all outside the White House gates — many of whom he consults at least once a week.

The media mogul Rupert Murdoch is on the phone every week, encouraging Mr. Trump when he’s low and arguing that he focus on the economy rather than detouring to other issues. The developer Richard LeFrak is a soothing voice who listens to Mr. Trump’s complaints that cost estimates for the border wall with Mexico are too high. Sean Hannity tells the president that keeping promises on core Republican issues is crucial.

Mr. Trump’s West Wing aides, like President Bill Clinton’s staff two decades before, say they sometimes cringe at the input from people they can’t control, with consequences they can’t predict. Knowing these advisers — who are mostly white, male and older — is a key to figuring out the words coming from Mr. Trump’s mouth and his Twitter feed.

Here, based on interviews with more than a dozen friends, top aides and advisers inside and outside the White House, are 20 of Mr. Trump’s outside touchstones.

The Mogul

Rupert Murdoch

Mr. Trump’s relationships depend on two crucial measures: personal success and loyalty to him. Mr. Murdoch excels in both categories. His New York Post vaulted Mr. Trump from local housing developer to gossip-page royalty, and his Fox News Channel was pro-Trump in the 2016 general election.

The two share preferences for transactional tabloid journalism and never giving in to critics. (Mr. Trump said the fallen Fox star Bill O’Reilly should not have settled sexual harassment complaints.) The president’s relationship with Mr. Murdoch is deeper and more enduring than most in his life, and the two commiserate and plot strategy in their phone calls, according to people close to both.

Mr. Murdoch even called the White House press secretary, Sean Spicer, to buck him up after Mr. Spicer was savaged for a remark about Adolf Hitler.

The Media

Sean Hannity

Presidents always deploy surrogates to appear on television to spout their talking points, but Mr. Trump has expanded on that by developing relationships with sympathetic media figures like Mr. Hannity who also serve as advisers. Mr. Hannity, the Fox News host, defends Mr. Trump’s most controversial behavior in public, but privately, according to people close to Mr. Trump, he urges the president not to get distracted, and advises him to focus on keeping pledges like repealing the Affordable Care Act.

Chris Ruddy

The chief executive of Newsmax Media is a longtime Mar-a-Lago member and was a Trump cheerleader among conservative media well before the website Breitbart joined the parade. He employs writers and editors who tracked Mr. Trump’s career when they were at The New York Post. He recently visited the Oval Office, and he and Mr. Trump kibitz in Florida and by phone.

The Lawyer

Sheri A. Dillon

Ms. Dillon seemed out of place when she spoke at a too-large lectern in the lobby of Trump Tower on Jan. 11, describing the steps Mr. Trump planned to take to separate himself from his business. But Ms. Dillon, a tax lawyer who worked out a highly criticized plan for Mr. Trump to retain ownership of his company but step back from running it, has repeatedly counseled the president about the business and made at least one White House visit. (Michael Cohen, a veteran Trump aide, has been serving as his personal lawyer.)

Campaign Advisers

Corey Lewandowski

Despite his “you’re fired” slogan, the president dislikes dismissing people. Mr. Lewandowski, Mr. Trump’s hot-tempered first campaign manager, was fired in June but never really went away. A New England-bred operative whose working-class roots and clenched-teeth loyalty earned him Mr. Trump’s trust, he continued to be in frequent phone contact with Mr. Trump until the election and beyond. Friends of Mr. Lewandowski say that he can see the windows of the White House residence from his lobbying office on Pennsylvania Avenue, and that the view is even better during his visits to the West Wing, including when the New England Patriots were there this past week.

Newt Gingrich

The former House speaker talks more with Mr. Trump’s top advisers than he does with the president, but his presence permeates the administration. Mr. Gingrich’s former spokesman is at the State Department, and two former advisers work in the West Wing. Mr. Gingrich has relentlessly promoted Mr. Trump’s policy adviser, Stephen Miller, as the West Wing conservative ballast as the chief strategist, Stephen K. Bannon, has been under fire.

Image President Trump in the Roosevelt Room this week. Outside the White House, Mr. Trump has kept a small group of informal advisers whom he speaks with at least one a week. Credit... Al Drago/The New York Times

Childhood Friend

Richard LeFrak

Their fathers were developers together in New York, and the two men have been friends for decades. Mr. LeFrak is a Mar-a-Lago member, and he agreed to be part of an infrastructure effort that Mr. Trump hopes to put forward. Mr. Trump has turned to him to vent frustrations about the slow pace of bureaucracy.

The Peers

Thomas Barrack Jr.

Mr. Trump divides the people around him into broad categories: family, paid staff and wealthy men like Mr. Barrack whom he considers peers. A sunny and loyal near-billionaire who has socialized with the president for years, Mr. Barrack is less a strategic adviser than a trusted moneyman, fixer and sounding board who has often punctuated emails to Mr. Trump with exhortations like “YOU ROCK!” He has urged Mr. Trump to avoid needless, distracting fights.

Under Mr. Barrack’s leadership, Mr. Trump’s inaugural committee raised a record $106.7 million, much of it from big corporations, banks and Republican megadonors like the Las Vegas billionaire Sheldon Adelson. Mr. Barrack also helped usher Paul Manafort, the international political operative now under scrutiny for his ties to Russia, into the Trump fold last year. The velvet-voiced Mr. Barrack does not seek out attention for himself, one of the most important and elusive qualities by which the president judges people.

Stephen Schwarzman

The chairman and chief executive of the Blackstone Group, Mr. Schwarzman is the head of Mr. Trump’s economic advisory council. He and the president don’t speak daily, West Wing aides said, but do talk frequently. Mr. Schwarzman has counseled him on a number of topics, including advising him to leave in place President Barack Obama’s executive order shielding young undocumented immigrants, known as “Dreamers,” from deportation.

Steve Roth

A good way to get on Mr. Trump’s side is to do a deal with him, particularly if it means rescuing him from his own financial crisis. That’s what Mr. Roth, a real estate tycoon, did a decade ago when he bought out Mr. Trump’s share in a West Side real estate deal that went sour. Mr. Roth, head of Vornado Realty Trust and a longtime Democratic donor, also helped Mr. Trump’s son-in-law, Jared Kushner, when he injected $80 million into 666 Fifth Avenue, a Kushner family property in danger of defaulting on $1.1 billion in loans. Mr. Trump speaks with Mr. Roth frequently, and is leaning on him to help develop a trillion-dollar infrastructure package expected this year.

Phil Ruffin

Mr. Trump has 20-odd business partners, but none is closer to him than Mr. Ruffin, 82, a Texas billionaire who has lent his ear and private jet. The president was best man at the 2008 wedding of Mr. Ruffin to his third wife, a 26-year-old model and former Miss Ukraine. Mr. Ruffin has a knack for showing up when Mr. Trump needs him most and remains a die-hard defender. “This stuff about him having financial investments all over Russia — that’s just pure crap,” Mr. Ruffin told Forbes. “I went to Russia with him. We took my airplane. We were having lunch with one of the oligarchs there. No business was discussed.”

Carl Icahn

Rounding out Mr. Trump’s roster of wealthy octogenarians is this 81-year-old corporate raider and real estate mogul, who occupies perhaps the most respected perch in the president’s circle of businessmen buddies. The affection is longstanding: The Queens-bred Mr. Icahn has known Mr. Trump and his family for decades. It’s also numerical: Mr. Icahn is worth an estimated $16 billion, a major plus in the eyes of a president who keeps score. Mr. Icahn serves as a free-roving economic counselor and the head of Mr. Trump’s effort to reduce government regulations on business.

Man of Mystery

Roger J. Stone Jr.

Few alliances in politics are as complicated as the 40-year relationship between the Nixon-tattooed Mr. Stone and Mr. Trump. Mr. Stone won’t say how frequently they speak these days, but he shares the president’s tear-down-the-system impulses and is ubiquitous on cable news, radio and the website InfoWars defending Mr. Trump.

The Clubgoers

Ike Perlmutter

Mr. Perlmutter, the chief executive of Marvel Comics, who is so reclusive that there are few public photographs of him, has been informally advising Mr. Trump on veterans issues. The two men are old friends, and Mr. Perlmutter has been a presence at Mar-a-Lago.

Robert Kraft

The owner of the New England Patriots is a Democrat, but his loyalty to Mr. Trump, Mr. Kraft once said, dates partly to the president’s thoughtfulness when Mr. Kraft’s wife died. Mr. Trump loved talking about the Patriots during the campaign, and Mr. Kraft has been a Mar-a-Lago presence since the transition.

The First Lady

Melania Trump

Mrs. Trump is uninterested in the limelight, but she has remained a powerful adviser by telephone from New York. Among her roles: giving Mr. Trump feedback on media coverage, counseling him on staff choices and urging him, repeatedly, to tone down his Twitter feed. Lately, he has listened closely, and has a more disciplined Twitter finger.

The Governor

Chris Christie

Mr. Kushner, the president’s son-in-law and palace gatekeeper, has shown a capacity to hobble his rivals, but few have been finished off. The most durable has been Mr. Christie, whose transition planning, several West Wing aides now concede, should not have been discarded. He has been a frequent Oval Office visitor and has worked with the White House on the opioid addiction crisis.

The Speaker

Paul D. Ryan

Mr. Trump and the clean-cut and wonky Wisconsinite aren’t exactly best friends forever. But their relationship is closer than in the bad old days of the 2016 campaign when Mr. Ryan delayed a hold-my-nose endorsement of Mr. Trump, whose morality he had long questioned. But as the president’s agenda passes through the razor-blade gantlet of the House, where Mr. Ryan faces the constant threat of opposition and overthrow, the two men have become foxhole buddies.

The Sons

Donald Trump Jr. and Eric Trump

The two sons and the president insist they no longer discuss company business. But the family is close, and Mr. Trump still speaks to his sons frequently, inquiring about their lives and searching for gut-checks on his own.