Nunes, Schiff and others at the heart of the FISA memo clash

The House Intelligence Committee, investigating Russian interference in the 2016 election, fell into further partisan divide after the release of a controversial memo that alleged federal surveillance abuses in the spying of President Trump’s former associates.

The initial memo released by Republicans on the committee detailed purported improper surveillance by the FBI and Justice Department officials to spy on Carter Page, a foreign adviser for Trump during his campaign.

Less than a month later, Democrats on the committee released their own memo, although it contained heavy redactions. The rebuttal memo was meant to counter claims in the Republicans’ document.

As the memo clash continues, here are the names you should know.

Devin Nunes

Rep. Devin Nunes, R-Calif., is the chairman of the House Intelligence Committee, serving in that role since 2015.

Nunes, 44, was one of the authors of the GOP memo released earlier this month that detailed the alleged surveillance abuses. He told Fox News he had an “obligation to the American people” to make FISA abuses public.

“I think the American people understand that the FBI should not go to secret courts using information that was paid for by the Democrats to open up investigations, get warrants on people of the other political party. That’s the type of stuff that happens in banana republics,” Nunes said.

Before the memo was released, Congress voted to reauthorize Section 702 of FISA. While that particular section wasn’t used to obtain the warrant detailed in the memo, lawmakers have still pointed to it as a “dangerous” example of how FISA can lead to violations against Americans’ Fourth Amendment rights.

Nunes voted to reauthorize that section earlier this year.

Trump has said Nunes "may someday be recognized as a Great American hero for what he has exposed and what he has had to endure."

Adam Schiff

As the top Democrat on the committee, Rep. Adam Schiff, D-Calif., came out swinging at the GOP’s memo, calling it “misleading.”

Schiff, 57, and other Democrats on the committee created their own rebuttal memo which was released – along with heavy redactions – in late February. The memo countered the GOP narrative that the FBI and Justice Department conspired against Trump as they investigated his ties to Russia.

Schiff said his party’s memo is “the product of good faith negotiation between the Minority and the FBI and DOJ.”

Schiff is a former assistant U.S. attorney who helped prosecute the first FBI agent to be convicted of espionage for leaking secret documents to the Soviets.

Trump has lambasted the lawmaker, whom he called “Little Adam Schiff,” claiming he is “desperate for higher office” and “one of the biggest liars and leakers in Washington.”

Christopher Steele

At the heart of the GOP memo’s surveillance abuse claims is the now-infamous dossier compiled by ex-British spy Christopher Steele.

The GOP memo alleged that the dossier was key to the FBI’s FISA warrant in targeting Page. It also said the political origins of the dossier were not disclosed to the FISA court in the application or renewal process – something critics of the memo have denied.

The Democratic memo contended the Justice Department disclosed “the assessed political motivation of those who hired him” and that Steele was likely hired by someone “looking for information that could be used to discredit” then-candidate Trump's campaign.

Steele was hired by political firm Fusion GPS to compile opposition research on Trump, leading to the colorful but unverified dossier. The Democratic National Committee (DNC) and the presidential campaign for Hillary Clinton hired Fusion GPS through law firm Perkins Coie.

However, Clinton reportedly was unaware of the dossier until BuzzFeed News published it in January 2017.

Prior to the dossier dustup, Steele was an intelligence officer with Britain’s MI6 agency, serving in various countries, including Russia and France. Eventually, he co-founded Orbis Business Intelligence, an intelligence consulting agency.

Carter Page

FBI and Justice Department officials were able to obtain a FISA surveillance warrant on Carter Page, a former Trump campaign adviser, due to the controversial dossier, according to the GOP memo.

Page served as a foreign policy adviser to the campaign for a few months, although White House officials have sought to downplay the role he played.

He told Fox News he “became a liability pretty quick” for the campaign because of his Russian connections.

Page spent several years in Moscow, where he opened a Merrill Lynch office, according to the biography on the company’s website. He bragged in a 2013 letter that he was an “informal adviser” to the Kremlin, Time reported.

And Russian intelligence agents once unsuccessfully tried to recruit Page as a spy in 2013, Foreign Policy reported.

Page has told Fox News that he did “nothing that could even possibly be viewed in helping [Russians] in any way.”

But in a statement following the release of the Democrats’ memo, Schiff said, “The FBI had ample reason to believe that Carter Page was acting as an agent of a foreign power based on his history, including the fact that he had previously been a target of Russian recruitment, his travel to Russia, and other information.”

Lindsey Graham and Chuck Grassley

Republican Sens. Lindsey Graham and Chuck Grassley sent a criminal referral in early January for Steele, which was recently released. The pair’s referral appears to support some of the claims made in the GOP memo.

In their criminal referral, Graham and Grassley said the surveillance applications “relied heavily on Mr. Steele’s dossier claims.” They also said the applications “failed to disclose that the identities of Mr. Simpson’s ultimate clients were the Clinton campaign and the DNC.”

Grassley, the 84-year-old who represents Iowa, is the Senate Judiciary Committee chairman. Graham is a member of the committee as well.

“The American people now have some context for what they have been reading in the press for months, including some of which served as the basis of the criminal referral of Mr. Steele made by Senator Grassley and me,” Graham, the 62-year-old from South Carolina, said in a statement. “Through my service on the Senate Judiciary Committee, I have been investigating this matter for months, and will continue to do so.”

Michael Horowitz

The inspector general of the Department of Justice was appointed to investigate allegations of government surveillance abuse following the release of the memos.

Michael Horowitz has already been conducting a review of the FBI and Justice Department’s handling of the investigation into Hillary Clinton’s personal email server.

“We believe the Department of Justice must adhere to the high standards in the FISA court,” Attorney Gen. Jeff Sessions said in February. “Yes it will be investigated. And I think that's just the appropriate thing the inspector general will take that as one of the matters he'll deal with.”

 Bob Goodlatte and Trey Gowdy

Republican Reps. Bob Goodlatte and Trey Gowdy have requested Sessions appoint a special counselor to investigate certain decisions made by Justice Department officials in 2016 and 2017.

The call for a special counsel appears to have stemmed from the FISA memos.

Goodlatte, from Virginia, told Fox News the case for which the FISA warrant was obtained was “highly suspect.”

In their request to Sessions, the congressmen wrote, “There is evidence of bias, trending toward animus, among those charged with investigating serious cases.”

“There is evidence political opposition research was used in court filings. There is evidence this political opposition research was neither vetted before it was used nor fully revealed to the relevant tribunal,” they added.

Gowdy is the chairman of the House Oversight Committee; Goodlatte chairs the House Judiciary Committee. Both men are not seeking re-election in 2018.

Fox News' Brooke Singman and The Associated Press contributed to this report.