Carlo Allegri/Reuters Paul Manafort, Donald Trump's campaign chairman, told The Huffington Post in May that “This is not a hard race,” but things have changed since then.

WASHINGTON ― This spring, as he was becoming chairman of Donald Trump’s campaign, Paul Manafort told friends that the candidate knew all about his work for foreign leaders and thought the criticism he received for it was a “badge of honor.”

That was May. Now, in the heat of August ― after a series of investigative reports on Manafort’s activities in Ukraine ― he is on the losing end of a power struggle in the Trump camp.

The Republican presidential nominee has not stepped forward publicly to defend Manafort, and it’s not clear whether Trump knew that Manafort’s work might have had an unregistered (and therefore, potentially illegal) U.S. lobbying component.

Manafort may stay on as campaign chairman, but the operational power has shifted elsewhere.

The Ukraine implosion comes at the end of a particularly chaotic month, even by Trump standards, in which the campaign Manafort was ostensibly running committed mistake after mistake and plummeted in the polls.

Many of those mistakes were of the candidate’s own doing ― but they begged the question of whether Trump was being managed at all. Meanwhile, the campaign’s lack of a ground game, trips to non-competitive states and steady streams of Republican defections begged the question of whether Manafort was up to his job.

His enemies within the Trump circle, let by ousted campaign manager Corey Lewandowski, never thought so. Consistently, and often publicly, they worked to undermine whatever real authority Manafort had.

In an interview with The Huffington Post in late May, a confident-seeming Manafort bragged prematurely about his success. “This is not a hard race,” he said, citing Trump’s blue-collar appeal and Hillary Clinton’s unpopularity. Trump would not need to put a woman or minority on the ticket and would not need to significantly change his message or methods, just cut down on unforced errors and do a good job in the fall debates.

But on Manafort’s watch, the race has turned into a difficult, if not impossible, one.

Why?

For one, Trump remains unmanageable, especially when advised to rein in his pugilistic, if not deliberately offensive, campaign style.

Manafort had reason to know this from the start ― and reason to know that his advice would be ignored.

The taco bowl incident, trivial though it was, is one example. On Cinco de Mayo, Trump happened to be eating a taco bowl for lunch at his desk in Trump Tower. Manafort was in the office with other aides when a member of the family suggested they tweet a picture of Trump enjoying his “Mexican” lunch.

Manafort politely suggested that this might be seen as condescending and cautioned against it. The tweet went out. Trump himself was delighted by the resulting controversy. “The people who were offended were people we wanted to offend,” he later said.

Happy #CincoDeMayo! The best taco bowls are made in Trump Tower Grill. I love Hispanics! https://t.co/ufoTeQd8yA pic.twitter.com/k01Mc6CuDI — Donald J. Trump (@realDonaldTrump) May 5, 2016

A super-confident bearing is essential in Manafort’s main trade, which involves advising foreign authoritarian leaders on how to win elections using old-style American tactics.

But the fact is that Manafort, as shrewd and capable as he is, never managed a presidential campaign, or any high-level American campaign effort. He is a master of conventions and delegate counting, which is an insiders’ game. He is not an outward-facing message, media and U.S. voting expert.

And the leading authority on social media and politics in the Trump campaign is Trump himself.

“Paul’s knowledge, such as it is, is about 20 years old,” said a longtime adviser to Trump, who declined to be identified and is not in the Lewandowski camp. “He doesn’t know the new demographics or the new media.”

Manafort is not known as a debate prep expert, either, which is why Roger Ailes has and will continue to informally advise Trump on debate strategy and other messaging matters.

Manafort has not dismantled ― has not been able to dismantle ― the early staff that Trump assembled with Lewandowski, and Trump refused to help him do so.

Rather, the GOP presidential nominee maintains a floating array of power centers around him. His office can be crowded with sub-groups vying for attention, undercutting each other. He plays them off against each other, which allows him to keep his options open and deny chain-of-command responsibility that a hierarchy would impose.

The almost casual circumstances of Manafort’s hiring added to the uncertainty of who ran what. Trump had known him for years (Manafort has a condo in Trump Tower), and Manafort was recommended to Trump most forcefully and effectively by their longtime mutual friend, international businessman Tom Barrack.

Manafort is donating his services as chairman. It’s not clear why, except that it gives both him and Trump a reason to part ways if that ever becomes necessary.

Now, it may be.

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims — 1.6 billion members of an entire religion — from entering the U.S.