The FBI used only a small part of the information provided by former spy. The Democratic memo said the application made "narrow use" of information from former spy Christopher Steele's sources.
It described multiple other categories of information, including years-long suspicions that former Trump campaign aide Carter Page was being recruited by Russian spies, and revealed that the FBI had interviewed Mr Page about his ties to Russian intelligence officials in March 2016.
By contrast, Republicans have portrayed Mr Steele's information as the central focus of the application, filed to the US Foreign Intelligence Surveillance Court.
The Republican memo said it formed "an essential part" of the application.
The Democratic memo also said that what the FBI did use from Mr Steele did not include the salacious parts of his dossier.
Instead, it said, the bureau chiefly relied on the dossier's claims that Page had met a Kremlin official as well as a close associate of President Vladimir Putin during a July 2016 trip to Moscow, during which the official offered to provide compromising information about Mrs Hillary Clinton to the Trump campaign.
The surveillance court knew that Steele's clients had a political motive.
The Republican memo complained that the Foreign Intelligence Surveillance Court was not told that the Clinton campaign and the Democratic National Committee had financed Mr Steele's research, suggesting that the judges were misled about the credibility of his information. Democrats have called that claim misleading because the judges were told of a political motive, just without specific names.
The Democratic memo provided a verbatim excerpt from the application, which stated that the FBI believed that Mr Steele had been commissioned by someone "likely looking for information that could be used to discredit Candidate #1's campaign", referring to Mr Donald Trump.
The wiretap of Page generated useful intelligence
When the Justice Department repeatedly sought the court's permission to renew the surveillance of Page, the Democratic memo said, it cited new infor-mation it was gathering through the wiretap.
"The court-approved surveillance of Page allowed FBI to collect valuable intelligence," the Democratic memo said. It asserted that the repeated renewals "demonstrate that the FBI collected important investigative information and leads by conducting court-approved surveillance". What that intelligence was, however, was redacted.