The Trump dossier is one of the most important and least understood elements of the Trump-Russia affair. It is important not just because its allegations are, as former FBI director James Comey said, "salacious and unverified," but because it:

appeared to offer evidence for some of the most sensational accusations that the Trump campaign colluded with Russians; involved a pro-Clinton organization paying investigators who paid Kremlin-linked Russians for allegations about Trump; and set Comey and Trump on a collision course when Comey chose to brief Trump about the dossier in a one-on-one meeting when Trump was president-elect.

The story of the dossier, if it is ever learned, could greatly affect the way we think about the Trump-Russia matter.

One key talking point whenever the dossier is discussed is that it "started with Republicans," that is, it was originally commissioned in fall 2015 by a GOP donor who hired a dirt-digging firm called Fusion GPS to look into candidate Trump. The story, now widely told, appears to come from what a "person familiar" with the dossier told the New York Times in January of this year:

The story began in September 2015, when a wealthy Republican donor who strongly opposed Mr. Trump put up the money to hire a Washington research firm run by former journalists, Fusion GPS, to compile a dossier about the real estate magnate's past scandals and weaknesses, according to a person familiar with the effort. The person described the opposition research work on condition of anonymity, citing the volatile nature of the story and the likelihood of future legal disputes. The identity of the donor is unclear.

In this version of the story, the GOP-begun dossier originally was conventional opposition research involving Trump's business dealings — it was not about Russia. The Republican donor, the story goes, lost interest as Trump wrapped up the GOP nomination. At that point, "Democratic supporters of Hillary Clinton," according to the Times, picked up the project. At about the same time, Russian hacking of the Democratic National Committee was in the news, and Glenn Simpson, the former Wall Street Journal reporter who runs Fusion GPS, shifted the Trump dossier project to Russia, hiring former British spy Christopher Steele for the job. So the Democratic part of the dossier story was the attempt to dredge up information on Russia.

As far as the origin of the dossier is concerned, the idea that it all started with Republicans has become conventional wisdom.

But there are a lot of well-connected Republicans who are quite skeptical of the story. Specifically, the GOP strategists most involved in the competing campaigns that were trying to stop Trump — Ted Cruz, Marco Rubio, Jeb Bush, the campaigns that were closely linked to big Republican donors and were hungry for any negative information they could use against Trump — say they knew nothing about the effort at the time and do not believe it was in fact begun by a Republican donor.

"I don't believe the mad Republican donor theory," said Mike Murphy, the veteran strategist who ran Jeb Bush's $118 million super PAC, noting he never used Fusion GPS and had no inkling that it was conducting oppo for a big GOP donor. "We had the biggest share of Republican major donors," Murphy continued. "They all gossip. One guy is for Christie, his partner is for Bush. They all talk to each other, and I think I would have heard about it. And I didn't."

Terry Sullivan, who ran Marco Rubio's campaign, told me he had never heard of Fusion GPS before the dossier became public in January of this year. And he doesn't buy the it-started-with-Republicans idea. "The reason it is not at all believable that a Republican was behind it is, nobody used [any information] from it," Sullivan said. "Everybody was pretty damn desperate at the end. If someone had a kitchen sink, they would have thrown it."

Jeff Roe, who ran the Ted Cruz campaign, also noted that Trump's opponents were increasingly desperate to stop him as the primary season wore on. If Fusion GPS were peddling sensational information about Trump, why wouldn't one of those campaigns have used it? Beyond that, the non-Trump Republican campaigns talked to each other; there was no wall of silence between them. "Nobody ever brought this up," Roe told me, saying he finds the idea that a Republican found dirt on Trump and never used it or offered it to the campaigns is "total BS."

John Weaver, the veteran Republican operative who ran the John Kasich campaign, told me he was not aware of Fusion GPS at the time. "No one ever approached us, no one offered to help us. No one associated with the Kasich campaign had anything to do with it," Weaver said. He learned about the dossier when it was reported in the press, Weaver added.

Another high-ranking campaign operative, who did not want to be identified, said, "I never heard anything about it. You'd occasionally hear whispers of another campaign looking at some particular [Trump] business deal, little nuggets here or there. But I never heard anything about this. Never."

Apart from the campaigns, there were Republican operatives who took part in an ad hoc anti-Trump effort that ramped up after the departures of Bush and Rubio left the race to Trump, Cruz and Kasich. One person deeply involved in the effort told me, "I don't believe the dossier had anything to do with the Republican world because I would have known about it. There's no way I would not have known. I just never heard boo about it."

But what if they are all wrong? What if a Republican was in fact involved in the start of the dossier but kept the information away from the GOP campaigns that might have stopped Trump? I found one GOP NeverTrump operative, who also did not want to be named, to whom Glenn Simpson offered a story in late March 2016. The story, the operative told me, was an entirely conventional bit of oppo about Trump's business dealings — nothing at all about Russia or anything related to that. The GOP operative had, and has today, no idea of who might have commissioned the research Simpson offered. But he's not aware of any Republicans who were involved, and he was quite familiar with rich, anti-Trump Republicans.

The whole episode was unremarkable, the person said, because the remaining campaigns and the anti-Trump movement received over-the-transom tips all the time. Trump did this, Trump did that. Very little of it ever panned out, and they had no sense of a big-money GOP effort behind it.

And even after the primary campaign ended with the withdrawal of Cruz and Kasich after the May 3 Indiana primary, the NeverTrump movement marched on in hopes of somehow denying Trump the nomination at the Republican National Convention. And yet the alleged Republican-sponsored Trump oppo did not surface in the days before the GOP met in Cleveland. "They would have wanted to drop it before that to mess with the convention," the operative said. But that did not happen.

Talking to the campaign operatives who were trying to defeat Trump in the primaries, there is a lingering sense of frustration at their inability to stop the front-runner. But that frustration turns to disbelief at the notion that some Republican, somewhere, was running an expensive, high-end opposition research operation on Trump and never told the opposing candidates about it.

"I just can't fathom that I wouldn't have heard beforehand," Terry Sullivan told me. "Go back to where we were all at in March, April, May, as a party — the one unifying factor of everybody I knew was, 'Dear God, how are we going to stop this guy?' It would have come out."

"Jeff Roe called me frequently between when Marco dropped out and Cruz dropped out," Sullivan continued. "If somebody had it, why wouldn't they have used it? Somebody had that information, but didn't want to give it to the last two people who had a chance to stop Trump? It would blow my mind that they had anything that they didn't use."

So what is the bottom line? It's possible the it-started-with-Republicans conventional wisdom is just wrong. Or it's possible there was a rogue Republican zillionaire who wanted to commission an extensive opposition research operation on Trump but not actually use the results of that research in the effort to stop Trump. Or it's possible there was a zillionaire who characterized himself as a Republican but had never been a part of any GOP circles that the veteran political operatives who ran the Cruz, Rubio, Bush, and other Republican campaigns would recognize. Whatever the case, the conventional wisdom about the origin of the Trump dossier does not tell the whole story.