WASHINGTON — In 1993, as a midshipman at the U.S. Naval Academy, Carter Page wrote an academic paper on the tension between the executive branch and Congress over national defense secrets.

"It is true that congressional leaks may be used as potent political devices," he concluded.

Twenty-five years later, Page, who spent a few months advising the Donald Trump presidential campaign, is in the middle of an epic Washington battle over the role of Congress, the use of classified information and the future of the special counsel's investigation into Russia's election interference effort.

Page is the central figure in the Nunes memo, which alleges that the FBI withheld key information from the judges who approved and renewed the bureau's application to place Page under secret surveillance. The memo, released Friday, was written by Republican staffers on the House Intelligence Committee and is named after the committee's chairman, Rep. Devin Nunes, R-Calif.

The once-top secret memo spells out what has long been reported: that the FBI suspected Page was a Russian agent, something he vociferously denies, even as he acknowledges having a relationship with the Kremlin. NBC News has reported that four separate federal judges signed off on the surveillance and the subsequent renewals.

What the memo does not make clear is whether Page figures prominently — or at all — in special counsel Robert Mueller's sprawling investigation into potential Trump campaign-Russia collusion, obstruction of justice and other related matters. Some law enforcement officials have told NBC News that Page is not a significant player in the investigation.

Page, who has made his living as an energy consultant, has been open about his ties to Russia and Russians. Last week Time magazine reported that Page had described himself as a Kremlin adviser, and he subsequently made public the 2013 letter in which he made the comment.

"Over the past half year, I have had the privilege to serve as an informal adviser to the staff of the Kremlin in preparation for their presidency of the G-20 Summit next month, where energy issues will be a prominent point on the agenda," the letter said.

Page says that is nothing to be ashamed of.

"The main 'issue' is a perennial misunderstanding about Russia that's continued throughout much of the past century, particularly in Washington," Page told NBC News last week.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

Page found his way to the Trump team via New York State Republican Party chairman Ed Cox, who said he knew Page from his volunteer work on the 2008 John McCain presidential campaign. Page became more widely known after Trump cited him by name during a March 2016 meeting with the Washington Post editorial board. By September 2016, controversy over his Russia ties had led the Trump team to disavow him, and he left his campaign role. The FBI surveillance of him began in October, according to the memo.

Carter Page, a former foreign policy adviser to Donald Trump, speaks at a news conference at RIA Novosti news agency in Moscow on Dec. 12, 2016. Pavel Golovkin / AP file

After graduating from Annapolis, Page spent 18 months in the Pentagon, acting, he says, as the Navy's working group representative on nuclear nonproliferation policy issues, focusing on negotiations with Russia. He served aboard an ammo ship and a frigate for three years, attended Surface Warfare Officers School in Rhode Island for two stints totaling seven months, and was a lieutenant in the Navy Reserve from 1998 to 2004. He was not promoted while in the reserves.

Page detailed his long history with Russia during a meeting with House investigators last November, starting with a June 1991 visit to Moscow as a Naval Academy midshipman. He learned to speak Russian enough to "get my ideas across," according to transcripts of the meeting, developed a relationship with a Russian university called the New Economic School, and in 2015 and 2016 worked on behalf of various clients wanting to do business in Russia.

In 1998 Page spent three months working for the Eurasia Group, a strategy consulting firm whose founder, Ian Bremmer, later called him the firm's most "wackadoodle" alumnus.

Carter Page going down as the most wackadoodle @EurasiaGroup alum in history. #SoFar — ian bremmer (@ianbremmer) April 13, 2017

Page moved to Moscow in 2004, where he became an energy consultant with Merrill Lynch. He told lawmakers he served as an adviser "for many years" for Gazprom, a Russian energy firm, where he developed a decade-long relationship with Andrey Baranov, who later joined Russia's state-owned energy company, Rosneft. He didn't rule out that his conversations with Baranov would have involved U.S. sanctions on Russia's energy sector.

Page said he acquired a financial interest in Gazprom some time in 2008, but he divested from it in the summer of 2016 while working on the Trump campaign, in response to what he learned were concerns about the investment raised to the FBI, he has said.

Most significantly, Page described to lawmakers two visits to Moscow in 2016 — first in July, at the height of the presidential campaign, and again in December, after a Foreign Intelligence Surveillance Act (FISA) court had granted a warrant for his surveillance.

Page said his July visit was centered around a speech at the New Economic School, at which he had what he described as a brief encounter with Russia's deputy prime minister. On that trip he also met with Baranov, and in response to Democrats' questioning did not rule out that their discussion included the topic of sanctions.

"Just like someone may have mentioned tax policy in November 2017 in Washington, there may have been an analogous brief mention [of sanctions] in Moscow in July 2016," he told the House Intelligence Committee.

Page said he was not acting on the trip as a surrogate of the Trump campaign, although he acknowledged informing Jeff Sessions, then a U.S. senator from Alabama and a top campaign official and now the attorney general, about the trip.

Page said his December trip was a personal one, which he paid for himself, and centered around his interest in business possibilities and "a general scholarly context." He again met with Baranov, and said the discussion ranged from energy markets to the just-concluded election. "Based on public information and nothing nefarious in any way," he added. On the same trip he also met in London with Russian nationals and the Kazakh ambassador to the U.K., discussing opportunities in the energy market there.

In his interview with the House Intelligence Committee, Page also confirmed he had "either four or five meetings" with FBI investigators in the spring of 2017, and that their questions focused on issues raised in the Steele dossier, named after the British intelligence operative who compiled it.

The FBI's interest in Page goes back at least to 2013, when he figured in a separate Russian-related espionage investigation.

Page was swept up in a spy probe involving Victor Podobnyy, an attaché at the Russian consulate in New York City. In 2015, Podobnyy was charged with espionage, accused of posing as a diplomat while trying to recruit Page as a Russian intelligence source. U.S. authorities alleged Podobnyy was an agent for the SVR, Russia's foreign intelligence service.

Page was described as "a male working as a consultant in New York City." Page last year confirmed he was the unnamed consultant and said he cooperated with the FBI. Court filings said Page had provided the Russians with documents about the energy sector, which Page said were innocuous.

Podobnyy said on an FBI wiretap that he considered Page "an idiot."

Page has been arguing for months that the Trump-Russia investigation was a cooked-up fraud based on a "dodgy dossier.

Now, some people are wondering whether Page knew in advance that congressional Republicans would follow his playbook.

In October, Page said on MSNBC's "All In With Chris Hayes": "When the truth comes out, when Speaker Paul Ryan says the FISA warrant, the details about the dodgy dossier, and what happened and all the documents around that is going to be released, that's what I'm really excited about and I think the truth will set a lot of people free."

On Monday, Page told NBC News via email: "I had no advance information. He made some comment PUBLICLY and I just referred to that. Nada mas amigo."