NEW YORK — He was a lobbyist who represented one client who sought funds from the federal stimulus program and then another, a group backed by the Koch brothers, who opposed it. He was a political operative who once debated a cardboard cutout of the Democratic governor of New Hampshire to protest tax rates.

And he was a congressional aide who was arrested after he brought a gun to work, then sued when he did not get it back.

Perhaps not surprisingly, the campaign manager for Mr Donald Trump’s unorthodox bid for president, Corey Lewandowski, a 40-year-old New Hampshire resident, does not have a conventional resume.

In searching for someone to steer his effort, Mr Trump went not to someone with a depth of experience in national elections, but to someone he appears to see as a kindred spirit: a deeply ambitious, sometimes-mercurial master of self-reinvention (Lewandowski has also been a New Hampshire state public safety officer and a real estate agent). And, like Mr Trump, exactly what his political leanings are beyond a belief in small government is uncertain.

Mr Lewandowski’s unconventional background is matched by his approach to running a campaign.mer

While some candidates look for a manager who will rein in their impulses, Mr Lewandowski channels them. He is not interested in telling Mr Trump what to do or in being a master strategist. His greatest trait, Mr Trump said in an interview, is that “he knows when to speak up.”

“He leaves me alone, but he knows when to make his presence felt,” Mr Trump said.

Mr Lewandowski spends his days travelling with the candidate or working out of his boss’ Trump Tower headquarters in Manhattan, putting together schedules, speaking with organisers in early-voting states and handling a staff that is mostly based elsewhere.

At one point, Mr Lewandowski was part of the fabric of establishment Washington, working for Rep Bob Ney of Ohio, and, later, with the Republican National Committee.

But, said David N Bossie, president of the conservative group Citizens United, who helped connect the candidate with his campaign manager, Mr Lewandowski “is as anti-establishment as Mr Trump.”

He is also relatively parochial, having spent most of his life in New England.

Even now, he tries to get home as much as he can to New Hampshire, where he lives with his family, and where the many Republicans who know him or know of him decline to speak ill of him for the record, even as a few privately question whether he is playing at a level that is over his head.

Mr Trump, who rarely brings new people into his small circle of advisers, has been content to let Mr Lewandowski consolidate power after the departure of Roger J Stone Jr, a long-serving adviser. Mr Stone has said that he had taken issue with the tone of the campaign, but that he still supports Mr Trump.

Mr Trump told one friend that he liked Mr Lewandowski “because he doesn’t get emotional.”

But that is not a view that is universally shared about Mr Lewandowski, who is known to have a temper and who had a mixed reputation at Americans for Prosperity, the group sponsored by Charles G and David H Koch he first represented as a lobbyist and for which he later went to work.

He held various jobs in the Kochs’ political world, including as a state director in New Hampshire and, last year, as the head of a national voter registration drive. He promoted the Kochs’ views of small government, which led to his stunt debating a cardboard cutout of Governor John Lynch of New Hampshire on national tax day in 2010.

After seven years with Americans for Prosperity, Mr Lewandowski moved on, leaving behind some fans who found him to be efficient and effective, but also some detractors, who found his abrasiveness off-putting.

Mr Lewandowski is hardly news-media-shy — he has been a frequent CNN guest promoting Mr Trump — but he is not eager to discuss himself. He declined requests for an interview.

A tall, reedy man with the features of a young Robert Duvall in “To Kill a Mockingbird,” with close-cropped hair, pale skin and dark circles under his eyes, Mr Lewandowski began his political career in his hometown, Lowell, Massachusetts, when he ran unsuccessfully for a state legislative seat in 1994.

A few years later, he ended up working for Mr Ney.

“I remember he was doing the interview, and he had a frayed cuff” on his shirt, Mr Ney said. “And I thought, ‘That’s just a regular working guy.’”

After the election, Mr Lewandowski went to work in Washington as Mr Ney’s chief of staff, and made headlines when he brought an unloaded gun into a House office building in the bottom of his laundry bag. He was charged with a misdemeanor. He said it was an accident, and his lawsuit, charging that he had been denied due process when his gun was taken away, was thrown out by a judge.

After Mr Ney was convicted of corruption charges in the Jack Abramoff lobbying scandal and forced to resign in 2006, Mr Lewandowski wrote a letter to the court defending him.

Mr Ney said his parents still asked about Mr Lewandowski, who was seen as a member of their family.

In 2002, Mr Lewandowski managed the re-election effort of Senator Bob Smith of New Hampshire, who had a complicated history with the Republican Party and who had switched his affiliation to independent when he briefly ran for president in 2000.

By the time Mr Lewandowski joined the re-election effort, establishment Republicans were trying replace Mr Smith with Rep John E Sununu, the son of a former governor.

“We lost, but I don’t blame him for that,” Mr Smith said of Mr Lewandowski.

During that race, the Smith camp raised questions about Mr Sununu’s credibility as a supporter of Israel (he has a Lebanese background), criticisms that the congressman’s allies saw as having anti-Arab undertones.

After Smith had lost, and with Lewandowski’s relationship with the party establishment frayed, he held different jobs, including working with the New Hampshire Department of Public Safety.

He then became a lobbyist with the government affairs firm Schwartz Communications in Massachusetts, taking on some clients interested in the stimulus spending program proposed by President Barack Obama and enacted by congressional Democrats to help the economy recover from the financial meltdown of 2008.

Another client was Americans for Prosperity, which has criticised the stimulus spending.

Mr Trump insisted that he had to woo Mr Lewandowski away from Americans for Prosperity. But he made clear that he was going to decide for himself how he was going to run.

“This is going to be a different kind of campaign,” he told his new hire. THE NEW YORK TIMES