But the memo also points to another individual with ties to the Trump campaign, George Papadopolous, as a key factor in the instigation of the FBI's Russia probe.
Papadopoulos, a young foreign-policy consultant who pleaded guilty in the special counsel's investigation, is now reported to be a cooperating witness.
"The Papadopoulos information triggered the opening of an FBI counterintelligence investigation in late July 2016 by FBI agent Pete Strzok," the memo noted in its final paragraph.
That timing is significant, given the FBI did not seek authorization to conduct surveillance on Page until three months later, on Oct. 21, 2016.
Democrats quickly seized on that sentence to assert the Republicans' own memo shows the Russia investigation would be underway with or without the surveillance of Page, and — more critically — even if the government had never seen the dossier of information about Trump that was compiled by Christopher Steele, a former British spy.
The dossier was funded by the Hillary Clinton campaign and the Democratic National Committee, fueling GOP claims that some underlying evidence used by the FBI was politically motivated and therefore illegitimate.
"The authors of the GOP memo would like the country to believe that the investigation began with Christopher Steele and the dossier, and if they can just discredit Mr. Steele, they can make the whole investigation go away regardless of the Russians' interference in our election or the role of the Trump campaign in that interference," Democrats on the House Intelligence Committee wrote in response to the memo, which was put together by the committee's Republican chairman, Devin Nunes (Calif.).
"This ignores the inconvenient fact that the investigation did not begin with, or arise from Christopher Steele or the dossier, and that the investigation would persist on the basis of wholly independent evidence had Christopher Steele never entered the picture," the Democrats added.
It also underscores what Democrats say is a disconnect between intelligence documents that have not been made public and the conclusions Republicans have drawn from them.
"Unlike almost every House member who voted in favor of this memo's release, I have actually read the underlying documents on which the memo was based," said Senate Intelligence Committee Vice Chairman Mark R. Warner (D-Va.). "They simply do not support its conclusion."
Even some Republicans cautioned against drawing too broad a conclusion from the memo and what it alleged about the initial motivations of the investigators.
The FBI's actions last year ultimately led to what has become a separate independent probe, which is being led by special counsel Robert S. Mueller III, who is himself a former director of the agency.
"As I have said repeatedly, I also remain 100 percent confident in Special Counsel Robert Mueller. The contents of this memo do not — in any way — discredit his investigation," Rep. Trey Gowdy (R-S.C.) tweeted. Gowdy, who announced Wednesday that he will not run for reelection, is an influential voice, given he led the politically charged House probe into the 2012 attack on the U.S. mission in Benghazi, Libya.
Papadopoulos appears nowhere in the 16 reports Steele wrote between June and December 2016 that are now known collectively as the Steele dossier.
Instead, people familiar with the matter have told The Washington Post that the FBI was first alerted to Papadopoulos from the Australian government in late July 2016, around the time WikiLeaks posted thousands of internal DNC emails online.
According to the Australians, Papadopoulos bragged to one of their diplomats during a boozy night at a London bar in May 2016 he had been told the Russians had emails that would be damaging to Clinton. The Australian connection was first reported by the New York Times.
The FBI ultimately interviewed Papadopoulos in January 2017 and then arrested him in June. He pleaded guilty in October to lying to the FBI about his Russia contacts and acknowledged he had been told by a London-based professor in March 2016 that the Russians had Clinton-related emails.