When President Trump first vowed to impose a 5 percent tariff on Mexico if it didn’t do more to stem the flow of migrants to the border, he told White House officials he wanted Peter Navarro on TV defending the plan.

The next morning, the presidential adviser appeared on CNBC and called the tariff threat “a brilliant move,” while preaching the trade protectionist gospel that has endeared him to Trump and earned him enemies across Washington and corporate America.

A week later, Trump announced a border deal with Mexico that avoided a trade war, and he has spent the days since extolling the virtues of tariffs.

The showdown with Mexico marks a high point in Navarro’s tumultuous tenure in the White House as Trump’s increasingly aggressive actions on trade, including toward China, mirror policies that the man he calls “my Peter” has pushed since the beginning of the administration.

Navarro, along with White House adviser and immigration hawk Stephen Miller, helped devise the proposed Mexican tariffs and beat back arguments from other aides that Trump did not have the legal authority to implement the trade penalties, and that the fight could derail the new trade deal with Mexico and Canada, according to White House aides. Like others interviewed for this story, they spoke on the condition of anonymity to discuss the internal debates.

Navarro’s ascension is frightening his critics, who have derided him as an ideologue who doesn’t let facts get in the way of his agenda, while cheering supporters of the president eager for Trump to emphasize his nationalist agenda ahead of his 2020 reelection campaign.

“Peter is a fierce warrior for my father’s America First trade agenda and while it may upset some members of the failed bipartisan establishment of the Washington Swamp, he understands that we can’t allow China to continue taking advantage of American workers and hollowing out our industrial base,” Donald Trump Jr. said in a statement to The Washington Post. “His only agenda is my father’s agenda and the White House is lucky to have him.”

The effectiveness of Navarro’s approach will be put to the test if Trump follows through on his threats and musings about implementing tariffs and tightening U.S. trade practices. The result of what has been done so far is unclear.

Trump still hasn’t inked final trade deals with Canada, Mexico, Japan, China or the European Union — all of which the president has claimed will be far better than anything agreed to under his predecessors. And while many indicators are still strong, there are signs that the economy is beginning to slow, a development that many economists and free-trade-supporting Republicans warn will be exacerbated if the president continues to follow a hard-line approach.

Also left unclear is whether Navarro, 69, can maintain his current level of influence with Trump as his critics inside and out of the administration try to get the president to soften his trade policies and warn that Navarro is a dangerous influence. His standing in the White House has vacillated several times during Trump’s presidency.

Since the beginning of the administration, Navarro who runs a five-person shop called the Office of Trade and Manufacturing Policy from the Eisenhower Executive Office Building near the White House has clashed with aides in most every area of the White House, including the communications staff, the staff secretary’s office, national security officials and aides in the vice president’s office, according to a senior administration official. He at times has also had a testy relationship with GOP senators who are wary of Trump’s adversarial, hard-line, against-the-Republican-grain approach to trade.

The White House declined to comment on any internal tensions regarding Navarro.

Navarro was at odds with then-White House National Economic Council Director Gary Cohn during the first year of Trump’s presidency and continues to have a tense relationship with Treasury Secretary Steven Mnuchin. Cohn regularly told the president that Navarro was lying to him, according to current and former advisers , such as when Navarro told Trump he could just remove himself from a trade agreement with South Korea.

“He just makes s--t up,” Cohn told the president in one 2017 meeting, according to former administration officials.

Navarro has engaged in a number of heated fights with Mnuchin over currency manipulation, particularly whether China is taking actions to prop up its economy at the expense of U.S. trade, making arguments that Mnuchin has loudly stated were not based in facts, current and former officials said. Trump continues to side with Navarro on the issue of whether and to what degree China manipulates its currency, according to people familiar with the discussions.

 Even Larry Kudlow, Trump’s easygoing top economic adviser who joined the White House in March 2018, has complained repeatedly about Navarro, aides familiar with his comments said.

Former staff secretary Rob Porter told others Navarro was the biggest offender of internal White House protocols — and his biggest problem, and that he spent considerable time blocking his ideas on tariffs, current and former aides said. While John F. Kelly was chief of staff, the president’s secretary Madeleine Westerhout was told to call Porter or Cohn if Navarro was trying to get into the Oval Office. During internal debates over imposing steel and aluminum tariffs, Navarro covertly brought industry CEOs to the White House without other administration officials learning about it so Trump could announce the trade penalties — a move that infuriated Kelly and angered other aides — because Navarro told the cable-chyron-obsessed president the steel tariffs would get him positive news coverage.

White House communications aides have at times strategized on how to keep Navarro off TV, current and former officials said, because he often makes problematic headlines. For example, Navarro said last year there was a “special place in hell” for Canadian Prime Minister Justin Trudeau — he was rebuked in the building and forced to apologize. 

Navarro has on several occasions drawn up executive orders that were scuttled by the staff secretary’s office for being legally fraught or unworkable, aides said, such as requiring U.S. companies who were going to move manufacturing facilities abroad to publicly disclose the moves in advance. 

Current officials said Navarro is regularly acerbic in meetings when he challenges others, sometimes in front of the president, and often tells fellow advisers that he represents the president’s agenda while they do not. Aides took particular glee last year when the website Axios found Navarro’s old writings, which showed he once believed in free trade. Navarro accused his enemies of plotting against him.

But with Trump’s continued support, Navarro has outlasted many of his internal rivals and remains unbowed when confronted by his remaining critics. Trump often asks where Navarro — a professor emeritus at the University of California at Irvine business school — is and summons him to meetings when other advisers try to keep him out of the loop, according to aides. The president has told complaining senators and advisers that he likes Navarro and they are wrong about tariffs when they raise concerns, the aides said.

The two men first corresponded in 2012 after Trump read “Death by China,” a 2011 book co-authored by Navarro, and he later joined the campaign as an economic adviser and then moved into the White House. Navarro’s defenders dismiss the criticisms aimed his way as coming from people who don’t support Trump’s position on trade and argue that he is working to fulfill the president’s campaign promises.

“When we were building the campaign and formulating the president’s policy positions on China and trade, we relied on him very heavily. He was a natural to go into the government because he is unbelievably smart and truly believes what the president believes,” said Corey Lewandowski, Trump’s former campaign manager. “Is it the staff’s job to disregard what the president wants or implement it? Peter is working to implement what the president wants.”

Navarro is sensitive to his reputation as a controversial figure. While he declined to be interviewed for this story, several of his allies, a list that includes U.S. airline and steel executives, called The Post unprompted to praise him.

Peter Carter, the top lawyer at Delta, said that Navarro was key to pushing an “open skies” agreement that helps U.S. companies compete against foreign airlines. Retired Gen. Jack Keane, an informal Trump adviser who met with Navarro about the defense industry, said Navarro “has no bureaucracy in him whatsoever, and is trying to solve problems with a real intensity about him.”

Several Republican senators share a particular concern with Navarro’s views and influence. Two who are usually taciturn — Sens. Rob Portman (R-Ohio), a former U.S. trade representative, and recently retired Orrin G. Hatch (R-Utah) — have both gotten into heated debates with Navarro in Capitol Hill meetings and accused him of basing his arguments for tariffs on faulty premises, according to people familiar with the matter. A spokesman for Portman declined to comment.

Sens. Patrick J. Toomey (R-Pa.) and Tim Scott (R-S.C.) have also repeatedly complained about Navarro, according to people familiar with their comments. White House officials keep Navarro away from Senate lunches and meetings of the Senate Finance Committee after hearing complaints about him, current and former senior administration officials said.

Navarro has recently been trying to cultivate allies on Capitol Hill for a proposal supported by Trump, the Reciprocal Trade Act, that would give the president greater authority to impose tariffs if a country places them first on U.S. goods. This has agitated some White House aides because he has set up these meeting without getting clearance from the White House legislative affairs office, which usually arranges and oversees such visits. The proposal is not popular among many of Trump’s advisers.

But even those who have tangled with Navarro note he has survived multiple attempts to get rid of him and say that he understands the president better than many — and has only gained influence with the departure of other officials.

“Peter happens to have the same set of values that appeals to the president,” said Sen. Joe Manchin III (D-W.Va.), who has met with Navarro to discuss the president’s trade agenda. “It’s not that Peter tries to change the president’s mind. Basically, he’s found someone who is thinking along the same lines as him.”