Ben Carson is essentially ending his campaign. Here's how it all went wrong.

Ben Carson, the pathbreaking pediatric neurosurgeon turned Tea Party darling, plans to tell supporters he does not see a "path forward" for his campaign and will not attend Thursday night's Republican debate, according to a report in the Washington Post. He's not technically suspending his campaign — not yet, anyway — but he's essentially conceding it's over.

Carson entered the campaign as a long shot, mostly coasting on notoriety he's built up in conservative circles ever since he confronted President Barack Obama and assailed Obamacare at the 2013 National Prayer Breakfast.

He was an immensely appealing figure to the Republican base. He's not just black, but a bona fide hero in the black community, as Vox's Jenée Desmond-Harris explained last year. In a party that's struggled to reach nonwhite voters, that was huge. His work in neurosurgery, including separating twins conjoined at the head, was genuinely groundbreaking.

He had, by his telling, a Horatio Alger story of growing up poor in Detroit and using his smarts and willpower to pull himself out of it and into Yale and then medical school, which was music to the ears of economic conservatives eager to say it's possible to escape poverty through hard work.

The brief rise of the Carson campaign

The general view at the start of the campaign was that Carson was running for book sales. He has never worked in government, and doesn't have the money and demagogic skill of Donald Trump. A presidential bid could raise his profile and sell some books, maybe boost his speaker fees, but he surely couldn't win.

For a brief moment in the fall, however, he looked primed to win Iowa and at least give Trump a run for his money. After a long rise starting in June, Carson topped Trump in Iowa poll averages starting in early October:

His period in first place was brief — by October 31 Trump was edging him out again in Iowa — but for months he was second in national polls to Trump:

However, with good poll numbers comes scrutiny, and Carson withered in the face of it. At first, his problems were the typical ones that non-politicians faced. Like Herman Cain's 9-9-9 plan before it, Carson's biblically inspired flat tax proposal was roundly panned by people who actually know things about tax policy.

In a cringe-inducing Marketplace interview with Kai Ryssdal, and the CNBC debate on October 28, Carson struggled to explain how a flat tax of 10 percent (his original idea, inspired by tithing) or even the 14.9 percent tax he eventually settled on could come close to paying for the federal government. Estimates suggested it would leave the government $1 trillion a year short. Carson's answer was that he'd "close loopholes" and cut "wasteful spending," which isn't really an answer at all.

How conservatives fell out of love with him

The tax problem didn't undo Carson. Much weirder problems did. First, there were problems with his biography, the very thing that attracted so many to him in the first place.

In his autobiography, Carson recalls "punching a classmate in the face with his hand wrapped around a lock, leaving a bloody three-inch gash in the boy's forehead; attempting to attack his own mother with a hammer following an argument over clothes; hurling a large rock at a boy, which broke the youth's glasses and smashed his nose; and, finally, thrusting a knife at the belly of his friend with such force that the blade snapped when it luckily struck a belt buckle covered by the boy's clothes," to quote CNN's Scott Glover and Maeve Reston.

But when Glover and Reston spoke to nine friends, classmates, and neighbors who grew up with Carson, none of them recalled Carson being that violent. "I don't know nothing about that," classmate Gerald Ware told CNN. "It would have been all over the whole school."

The Carson campaign vociferously disputed the reports, insisting that he was too a pathologically violent teenager, leading to totally accurate headlines like, "Ben Carson Defends Himself Against Allegations That He Never Attempted to Murder a Child."

Worse still, it came to light that while Carson claimed he was offered a "full scholarship" to West Point, he never even applied there. This led to some strange arguments about the meaning of the word "scholarship" but in any case it contributed to the sense that Carson was embellishing his life story for effect. And given how central that life story is to his appeal among conservatives, the perception that it was exaggerated or outright false was devastating.

The other problem was that Carson's beliefs were wackier than anybody expected. He didn't just have a magical tax plan: He thought Joseph of Amazing Technicolor Dreamcoat fame built the Egyptian pyramids to store grain; he thought the Holocaust happened because of gun control; he thought Vladimir Putin, Palestinian President Mahmoud Abbas, and Iranian Supreme Leader Ayatollah Ali Khamenei were college buddies. Some of this stuff could fly on the more fringe end of the Tea Party movement, but the pyramid controversy in particular is just much stranger than the kind of stuff that, say, Ted Cruz would embrace.

It left the impression that Carson wasn't just inexperienced or in over his head, but actually a straight-up crank. My personal theory was that his politics have a lot in common with the conspiracism of 2009-'10 Glenn Beck (though even that doesn't explain the pyramid thing). But whatever the real explanation, it was a bit much for even base voters to stomach.

It was also not what they were looking for in the wake of the Paris and San Bernardino attacks. Carson's amateurishness really did become a problem then in a way it hadn't before. He made blunder after blunder: He said China was intervening in the Syrian civil war (it's not). He called the San Bernardino attacks a "hate crime," explaining, "Well it’s hard to imagine that you would shoot a bunch of people and not hate them, right?"

Even his own advisers thought he was out of his depth. Duane Clarridge, a former CIA operative and Carson adviser, told the New York Times, "Nobody has been able to sit down with him and have him get one iota of intelligent information about the Middle East."

The big, spectacular collapse of the Carson campaign

And so the campaign went into free fall. Poll numbers plummeted. Internally, havoc ensued. The campaign had raised a decent amount of money, but it was spending much of it on more fundraising, operating more like a pyramid scheme than an actual campaign. Around Christmas, Carson declared that he was shaking up his campaign, before flip-flopping the same day and saying all was well. His campaign manager, Barry Bennett, first heard of the impending shake-up from an Associated Press reporter.

A week later, Bennett and communications director Doug Watts quit the campaign, saying that Carson was only listening to one person: his friend and business manager Armstrong Williams, a conservative columnist previously most famous for taking money from the Bush administration in exchange for favorable columns.

Bennett also questioned whether the man whose campaign he ran was qualified for the White House: "You have to surround yourself with good people," Bennett said. "And he hasn't demonstrated that he can do that. No one wants Armstrong Williams anywhere near the Oval Office."

It appeared that Williams had taken over as Carson's main adviser, but apparently even that relationship is shaky. The Wednesday before the Iowa caucuses, Carson told reporters that Williams was a habitual liar: "Armstrong is not necessarily the epitome of truth. He doesn’t speak all things that are correct. He often speaks without thinking. He has no official capacity in the campaign whatsoever. His influence has been vastly overrated."

Unsurprisingly, a campaign this dysfunctional did not reach the early states with anywhere near the support or organization to finish well. Ultimately, Carson's campaign resembled Michele Bachmann's in 2012: a sudden unexpected rise, followed by a sharp fall when it became clear they were not ready for the big leagues.

Watch: The Republican Party is broken