Macgregor and Tata did not respond to requests for comment. A spokesperson for the National Security Council also did not respond to a query from POLITICO.

Defense Secretary Mark Esper has expressed reservations about Macgregor, who is a lightning rod in military circles, according to one of the administration officials. The West Point graduate is revered by some fellow former officers and analysts as a renegade who made a career out of questioning orthodoxy in the Army and for his contention that the military leadership has never been held accountable for the failures in Iraq and Afghanistan.

But Macgregor also has an army of detractors who see him as an opportunist still bitter that his ideas were not adopted and that he was not promoted to the rank of general like some of his peers. And they also question whether he has a well-developed worldview for such an important policy writ.

Macgregor would be a controversial choice to head the Pentagon’s policy shop. He was one of the most vocal critics of the military strategy in Iraq and was particularly disdainful of then-Gen. David Petraeus, whom he saw as a media darling, prima donna and battlefield failure.

His supporters assert Macgregor’s opposition to overseas military engagements is the best evidence of his good judgment over the years, and why he is a perfect fit to work for Trump, who has made it a priority to wind down America’s open-ended military commitments in the Middle East.

“I've seen Doug under fire in direct combat and I’ve seen him be right, time after time, on the most consequential foreign policy issues of the past two decades,” said Daniel Davis, a retired Army lieutenant colonel who famously publicly opposed an extended U.S. mission in Afghanistan.

“As important, no one is more skilled at being able to translate Trump’s best foreign policy instincts into successful policy,” added Davis, who is now a senior fellow at Defense Priorities, a think tank that advocates against an interventionist foreign policy.

“Too many senior advisers over the past three years have been more interested in trying to bend Trump’s views to match their own instead of faithfully executing his,” he said.

Others who know Macgregor and have watched his career closely have a very different take.

“He enjoys being a contrarian,” said retired Army Col. Andrew Bacevich, a fellow former armor officer and longtime international relations professor who is president of the Quincy Institute for Responsible Statecraft. “He gets great joy in skewering senior military officers. He thinks the four-stars are stupid.”

But that’s not going to help him if he ends up becoming Pentagon policy chief.

“Although it certainly is true that an undersecretary of defense for policy has a wide mandate,” Bacevich said, “I think it’s also true that the individual holding that office needs to have working relations with the senior military."

The bigger question, several said, is whether he is qualified for the post.

“What is his worldview,” asked a former colleague, who said Macgregor has published few insights into his views on America’s role in the world or the recent National Defense Strategy. The person asked to remain anonymous because he still deals with the Pentagon. “I’m just not aware of any of that. And I am a reasonably assiduous reader of this stuff. Some of us get paid to do that.”

But in recent months, Macgregor has been writing about a wider range of issues — from how Trump should deal with Russian President Vladimir Putin, the turmoil with Turkey and the future of NATO.

“Basically, you are the Defense secretary’s secretary of state,” said Thomas Ricks, a journalist and military historian, of the undersecretary for policy position. “What is his expertise besides armored warfare?”

Tata, meanwhile, is an avid Trump defender who regularly appears on Fox News, and is a novelist known for writing the "Threat" adventure series. He has been featured in Trump tweets for lauding him on the cable network, where he has defended the president for sending troops to the U.S.-Mexico border and for the firing last year of Navy Secretary Richard Spencer after he resisted Trump’s efforts to intervene in the legal case of former Navy SEAL Eddie Gallagher.

“President Trump is fulfilling campaign promises,” Tata wrote last year on Fox’s website. “He is acting consistently with what he said he would do on the campaign trail. Ultimately, the president is a nationalist in the best sense of word — a patriot who wants the best for his nation and all our citizens — not someone hostile to other parts of the world, as the distorted leftist rewrite of the term falsely asserts.”

Tata was particularly outspoken on Trump’s decision to fire Spencer over his handling of Gallagher’s war crimes case. Gallagher was accused of shooting civilians and fatally stabbing a wounded captive with a hunting knife, but was acquitted by a military jury last year of all but one charge and granted clemency in November by Trump.

“As Spencer and his hashtags fade over the next several days, the president’s support of warfighters over bureaucrats will increase the morale of those in the rank and file,” Tata wrote in another piece on Fox’s website. “The critics will angrily accuse the president of supporting a war criminal, but the real crimes in this case have been papered over by a secretary of the Navy eager to avoid embarrassment at the expense of a sailor who, on the whole, served honorably.”

On sending troops to the border, Tata also told Fox that “the left has an immediate visceral reaction in the opposite direction to anything that President Trump does for a lot of different reasons.”

Tata retired from the Army in 2008 under mysterious circumstances, after an Army probe found he had been having affairs with “at least two” women. He served as North Carolina transportation secretary but resigned in 2015, citing a need to spend more time with his family and the demands of his side career as a novelist. He also considered running for Congress.

Elbridge Colby, a former deputy assistant secretary of defense in the Trump administration, was also in contention for the job, but took himself out of the running, one of the administration officials said.