Carter Page is a former Trump campaign foreign policy adviser whose surveillance by the FBI is at the center of a declassified Republican memo released by House Intelligence Committee Republicans Friday. He's one of several Trump campaign associates who have been under scrutiny by the FBI and by lawmakers probing Russian meddling in the 2016 presidential election.

The memo focuses in part on the Foreign Intelligence Surveillance Act (FISA) warrants that authorized the surveillance of Page. Federal law enforcement sources as well as congressional sources briefed on the intelligence during the 2016 campaign have said that well before Page joined the Trump campaign, there were concerns about his contacts with Russian spies. The memo aims to connect information gathered for the Trump "dossier" alleging links between Donald Trump and Russia, to those FISA warrants.

After the memo was released, Page released a statement praising GOP congressional leaders for releasing the memo and suggested he'd use some of the information in it to update "my pending legal action in opposition to DOJ this weekend in preparation for Monday's next small step on the long, potholed road toward helping to restore law and order in our great country."

The GOP-authored memo says that on Oct. 21, 2016 the DOJ and FBI sought and received a FISA probable cause order authorizing electronic surveillance on Page. The FBI and DOJ obtained three FISA warrants targeting Page and three FISA renewals, according to the memo.

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Then-FBI Director James Comey signed three FISA applications in question on behalf of the FBI, and Deputy Director Andrew McCabe signed one, according to the memo. The memo says then-Deputy Attorney General Sally Yates, then-Acting Deputy Attorney General Dana Boente, and Deputy Attorney General Rod Rosenstein each signed one or more FISA applications on behalf of the DOJ.

Who is Carter Page?

Page was a little known investment banker when Mr. Trump announced him as a member of his foreign policy advisory team early last year. Trump aides insist the president has no relationship with Page and did not have any dealings with him during the campaign.

His relationship with Russia began to draw scrutiny during the campaign after he visited Moscow in July 2016 for a speech at the New Economic School. While Page said he was traveling in a personal capacity, the school cited his role in the Trump campaign in advertising the speech.

Page was sharply critical of the U.S. in his remarks, saying Washington has a "hypocritical focus on ideas such as democratization, inequality, corruption and regime change." During this visit, Page was suspected of meeting with Russian officials, and later, in October 2016, the FBI and Justice Department sought and were granted the power to electronically wiretap Page.

Days later, Page talked with Russia's ambassador to the U.S. at an event on the sidelines of the Republican National Convention. Attorney General Jeff Sessions spoke with the Russian envoy at the same event, a conversation he failed to reveal when asked about contacts with Russians during his Senate confirmation hearings.

The campaign began distancing itself from Page after his trip to Russia, saying he was only an informal adviser. By the fall, he appeared to have cut ties to the Republican campaign.

It's unclear how Page got connected with the Trump campaign. One campaign official said Page was recruited by Sam Clovis, an Iowa Republican operative who ran the Trump campaign's policy shop and is now a senior adviser at the Agriculture Department. Those who served on the campaign's foreign policy advisory committee also said they had limited contact with Page.

But in a letter Page sent to the Senate intelligence committee in March 2017, he cast himself as a regular presence in Trump Tower, where the campaign was headquartered.

"I have frequently dined in Trump Grill, had lunch in Trump Café, had coffee meetings in the Starbucks at Trump Tower, attended events and spent many hours in campaign headquarters on the fifth floor last year," Page wrote. He also noted that his office building in New York "is literally connected to the Trump Tower building by an atrium."

Page, a former Merrill Lynch investment banker who worked out of its Moscow office for three years, now runs Global Energy Capital, a firm focused on energy sectors in emerging markets. According to the company's website, he has advised on transactions for Gazprom and RAO UES, a pair of Russian entities.His interest in Russia came about when he studied in Moscow while he was a Navy midshipman in the early 1990s, and later in his career, he also worked in Russia for a few years. Media stories have pointed out that Page is the sole employee of his firm, and a New York Times Magazine profile of Page said that his company's headquarters were a windowless "corporate co-working space" that he rents by the hour.

Page also briefly worked for the Eurasia Group. The president of the Eurasia Group, Ian Bremmer, memorably tweeted about Page in April 2017, calling him "the most wackadoodle @EurasiaGroup alumn in history. #SoFar."