As expected, there is a desperate last-minute fight going on over the release of the House Intelligence Committee "FISA abuse" memo. In a statement Wednesday, the FBI expressed "grave concern" over the memo, saying it contained "material omissions of fact that fundamentally impact the memo's accuracy."

Committee Chairman Devin Nunes hit back, at first accusing the FBI of making material omissions of its own by withholding information from Congress in the long fight over Trump-Russia documents. Later, Nunes specifically denied the "material omissions" charge, saying, "The memo contains all the relevant facts on FISA abuse."

Still later, Rep. Adam Schiff, the committee's top Democrat, tried to throw another wrench in the works by accusing Nunes of altering the memo after the committee voted to make it public, therefore making it a different document which must receive another vote before it can be released. Nunes responded that the changes were minor edits to correct grammar, plus one change to address an FBI objection, and another requested by the Democrats themselves. There will no doubt be more wrangling before the document sees the light of day.

Meanwhile, a key emerging criticism of the (still secret) memo is that one of its main accusations — at least one that has been publicly discussed — is that the Justice Department relied in part on the unverified, Clinton-funded, oppo-research Trump dossier to win a secret warrant to spy on sometime Trump campaign foreign policy adviser Carter Page. The critics say that by objecting to the treatment of Page, Republicans have staked their credibility and prestige on a sketchy character who had mysterious contacts with Russians. Is Page really someone Republicans want to defend?

"Remember, if the stories today have it right, the memo lunatics are saying the FBI had no right to spy on CARTER PAGE," Commentary editor John Podhoretz tweeted. "CARTER PAGE, people."

"A Pickett's Charge on behalf of Carter Page," added TPM's Josh Marshall. "Helluva hill to die on."

Perhaps the critics are right. Just as Nunes' detractors have not seen the memo, neither have his defenders, so no one on the outside can accurately describe its contents. Whatever the case, though, it's worth stepping back to look at Republican concerns about the Page affair, and what the memo might reveal about the FBI's pursuit of him, and what that might mean about the larger Trump-Russia investigation.

There were reasons for the FBI to notice Page. Described as an "energy executive," he lived for a time in Russia, was always trying to drum up business, often in Russia, and his name popped up in a case against three Russians who in 2013 were posing as businessmen and trying to recruit Americans to become Russian agents. The Russians apparently wanted to enlist Page, who in the end was not accused of any wrongdoing and has denied any contacts with the Russians beyond ordinary business communications. For their part, the Russians came to view Page as something less than a prize; one of them was captured on a wiretap calling him an "idiot."

So Page was no Russian agent, nor did he ever appear to be in danger of becoming a Russian agent. Nevertheless, the case put Page on the FBI's Russia radar screen.

Fast forward to March, 2016. Candidate Donald Trump was under a lot of pressure, and the target of some ridicule, for not having a group of foreign policy advisers. Many veteran Republican foreign policy hands had specifically refused to help Trump, and Trump had no big names, beyond then-Sen. Jeff Sessions, advising him.

On March 21, Trump met with the Washington Post editorial board and told them that he had formed a foreign policy advisory panel. The paper asked him who was on the list.

"Well, I hadn't thought of doing it, but if you want I can give you some of the names," Trump said. The second name he read aloud was "Carter Page, PhD." Within hours, Page's name was in Post reports on Trump's foreign policy team.

It does not take a rocket scientist to think that, once the FBI saw the Post reports, someone there said, Hey — Page is that guy from the case of those Russian agents. It's entirely reasonable that FBI officials would have found that interesting — and they did. Director James Comey and number-two Andrew McCabe personally briefed Attorney General Loretta Lynch on the list of Trump foreign policy advisers, including Page, according to U.S. officials familiar with the matter.

Fast forward again, this time to summer 2016. Page traveled to Moscow to give a speech on July 7, a trip that was reported in newspapers at the time. On July 19, Christopher Steele, the former British spy who compiled the Trump dossier, discussed Page's visit in a dossier installment. Steele's report that Page had gone to Moscow was true but not news — it had already been in the press. But Steele went on to report that during the trip Page met with Igor Sechin, head of Rosneft, Russia's giant state-owned oil company (and a man under U.S. sanctions), as well as with Igor Divyekin, a top official in the Putin government. The dossier said Sechin offered Page and/or other Trump associates millions of dollars in exchange for ending U.S. sanctions against Russia. If true, that would be a serious allegation, which Steele, although working for the Clinton campaign and the Democratic National Committee, decided to pass on to the FBI.

In late July, the FBI formally began a counterintelligence investigation of the Trump campaign. Some officials have anonymously told the press that the dossier, which the FBI did not verify, had nothing to do with the decision to start an investigation, that the decision was in fact the result of the (completely separate) George Papadopoulos case. But other officials have made a more convincing case that the dossier, and its discussion of Page, was indeed part of the reason the investigation was begun. In any event, precisely what triggered the investigation is not as important as the fact that the "salacious and unverified" (Comey's words) dossier became a significant part of the Trump-Russia investigation that unfolded in the fall of 2016, at the height of the presidential campaign.

It's not entirely clear how, but Democratic Sen. Harry Reid, then the minority leader, got word of the dossier's allegations about Page. On Aug. 27, Reid wrote a letter to Comey noting "a series of disturbing reports" that "a Trump advisor who has been highly critical of U.S. and European sanctions on Russia … met with high-ranking sanctioned individuals while in Moscow in July of 2016, well after Trump became the presumptive Republican nominee." It certainly sounded like Reid had been briefed on the Trump dossier's report on Page.

Two months passed. On Oct. 19, the FBI reportedly applied for a secret court warrant to wiretap Page. It is that application that House Republicans are reportedly concerned about, suspecting the FBI used the still-unverified dossier as part of the reason to put Page under surveillance.

One mystery, to outsiders at least, is why the FBI waited until mid-October to seek a warrant on a man they had deep suspicions about in July. (Page left the Trump campaign in the August-September timeframe; it's difficult to pin down a specific date.) Beyond that is the question of why the FBI sought to wiretap Page at all.

Maybe special counsel Robert Mueller knows all, but congressional investigators are still trying to figure it out. At the moment, the best they can do is theorize based on what they've been able to discover. Here is some of that theorizing:

In mid-October, with the election fast approaching, the FBI felt increasing pressure to act. There was already plenty of public criticism of the bureau over perceived disparate treatment of Hillary Clinton and Trump; the FBI took very public actions in the Clinton case but kept mum about any action on Trump and Russia. The FBI did not even publicly acknowledge that its counterintelligence investigation was taking place.

Meanwhile, the information from Steele kept coming. On Oct. 18, the day before the reported Page warrant, Steele wrote more on Page's alleged meeting with Sechin. Steele reported that a "trusted compatriot" of Sechin's "elaborated" on the "secret meeting" that had been confirmed to him by a senior member of Sechin's staff. Steele's hush-hush sources said Page had confirmed that "were Trump elected U.S. president, then sanctions on Russia would be lifted." Steele's sources also said Page "clearly implied" that he "was speaking with the Republican candidate's authority."

It was hot stuff. Although still unverified, perhaps it led FBI investigators to see Page as a more important part of the Trump campaign than he actually was. Hill investigators have been baffled by the FBI's apparent treatment of the "idiot" Page as a central player in the Trump-Russia affair, instead of an eccentric presence on the periphery with no connection to Trump, or even people close to Trump.

Or maybe they targeted Page for wiretapping because they could. Page had pre-existing contacts with Russian agents, handily outlined in a fairly recent court case. He was beyond question in Moscow in July. And the dossier said the Russians offered Page a corrupt bargain to end U.S. sanctions in exchange for millions of dollars. (One question not often asked: How was Page, not elected to anything and not even on anyone's staff, supposed to end U.S. sanctions?)

Put it all together, and Page was the easiest guy to go after. Plus, the wiretap would allow the FBI not just to listen to Page's phone calls but to read his emails, not only going forward from the date of the warrant, but going backward for as long as Page had kept them. If Page truly were the beating heart of a Trump-Russia conspiracy, then there would likely be email evidence the FBI could use.

Besides Paul Manafort, Page is the only other American known to have been targeted for wiretapping in the Trump-Russia probe. (Trump national security adviser Michael Flynn was famously picked up in a transition conversation with then-Russian ambassador Sergey Kislyak, but it was Kislyak who was under U.S. surveillance.) It is reasonable for Congress, and the public, too, to want to know more about the Page case and the unverified dossier that is an element of it.

So that is part of the reason Republicans have focused on the Page wiretap warrant. Going back to the critics' objections, though, it's reasonable to ask: Is that a bad idea? And even if Page was wiretapped in part on the basis of the dossier, should Republicans take up the fight against it?

One reason some Republicans cite for their interest is based in civil liberties: If they'll do it to Page today, they'll do it to you tomorrow.

But another motivation for some Republicans is the growing suspicion that the FBI simply botched a critical aspect of the Trump-Russia investigation, that the bureau acted without sufficient reason to believe Page was a significant figure in any alleged Trump-Russia collusion. In that scenario, FBI officials, acting on Page's history and the allegations in the dossier, convinced themselves they had a strong case and presented evidence to the FISA court without fully informing the court where it came from. They did it because the Trump-Russia affair was a high-profile case, the bureau's highest officials were involved, there were egos in the mix, there were some investigators who hoped to compensate for the FBI's treatment of Clinton by going after Trump as well, and as a result investigators were desperate to find any thread they could pull that might unravel what they thought was the biggest case in decades. Page was the thread they pulled.

Now, the thinking goes, that mistake reverberates through American politics every day as some Democrats seek to use the Trump-Russia affair to remove the president from office. That's reason enough for Congress to try to get to the bottom of it.