Rep. Adam Schiff, D-Calif., the top Democrat on the House Intelligence Committee, has been leading the charge against the GOP's memo, calling it a "political hit job" on the FBI.
"If the memo was really about oversight, committee members would want to read the underlying documents and bring in the FBI. Republicans voted against both," Schiff tweeted on Feb. 4, two days after the panel released the "surveillance" memo.
The four-page memo, released by the House Intelligence Committee chairman Rep. Devin Nunes, R-Calif., on Feb. 2 claimed the infamous Trump dossier "formed an essential part" of applications by the FBI and Justice Department to spy on onetime Trump campaign adviser Carter Page.
Schiff has called the Republicans' memo "shoddy" and "misleading," claiming it was released only to undermine Special Counsel Robert Mueller's Russia investigation.
"The president’s decision to publicly release a misleading memo attacking DOJ & FBI is a transparent attempt to discredit these institutions," Schiff added. "We'll fight to release our classified response."
Schiff requested the committee release Democratic members’ own 10-page memo, with the promise to send it to the Justice Department for redactions – and the committee did just that on Feb. 24.
In a statement, Schiff said the Democratic memo should "put to rest" any concerns about conduct by the intelligence agencies.
"Our extensive review of the initial FISA application and three subsequent renewals failed to uncover any evidence of illegal, unethical, or unprofessional behavior by law enforcement and instead revealed that both the FBI and DOJ made extensive showings to justify all four requests," Schiff said.
The memo's release comes after the White House told Democratic lawmakers the memo required certain redactions before it could be made public.
"The Democrats sent a very political and long response memo which they knew, because of sources and methods (and more), would have to be heavily redacted, whereupon they would blame the White House for lack of transparency. Told them to re-do and send back in proper form!" Trump tweeted after the rubuttal's release was halted earlier this month.
Here's what you need to know about Schiff, his notable career moves and his recent Twitter exchanges with the president.
Who is Adam Schiff?
As a graduate of Stanford University and Harvard Law School, Schiff started his career in law. He spent six years working in the U.S. Attorney's Office in Los Angeles.
During his time as assistant U.S. attorney, Schiff prosecuted the first FBI agent ever to be convicted of espionage for passing secret documents to the Soviets.
"This is a betrayal tinged with hypocrisy," Schiff said at the trial for former FBI agent Richard Miller, who was sentenced to 20 years in prison, The New York Times reported. "We have here an agent who did just exactly what he was supposed to protect against."
Eventually, Schiff moved on to politics.
He was elected to the California State Senate in 1996, serving four terms before heading to the House of Representatives. The Democrat has been serving in Congress since 2001.
In recent years, Schiff has shifted his focus to foreign policy and national security. He now sits as a ranking member on the House Intelligence Committee and was a member of the Benghazi Select Committee, according to a biography on his official website.
Schiff's reaction to the FISA memo
Schiff recently said he believed the White House may have been behind the memo in an attempt to interfere with the Russia probe.
"I think it’s very possible his staff worked with the White House and coordinated the whole effort with the White House," Schiff said in an interview with ABC's "This Week."
The president said the memo completely "vindicates" him in the Russia investigation, though he said the "Russian witch hunt" would most likely continue.
"There was no collusion and there was no obstruction (the word now used because, after one year of looking endlessly and finding NOTHING, collusion is dead)," Trump tweeted on Feb. 2. "This is an American disgrace!"
But Schiff said, while misleading, the memo was proof there was collusion with the Russians.
"Quite the opposite, Mr. President," Schiff replied on Twitter. "The most important fact disclosed in this otherwise shoddy memo was that FBI investigation began July 2016 with your advisor, Papadopoulos, who was secretly discussing stolen Clinton emails with the Russians."
Schiff versus Trump: The Twitter war continues
Trump targeted "Little Adam Schiff" on Feb. 5, calling him one of the "biggest liars and leakers in Washington," as both parties continued to argue over the newly released FISA memo.
"Little Adam Schiff, who is desperate to run for higher office, is one of the biggest liars and leakers in Washington, right up there with Comey, Warner, Brennan and Clapper!" Trump tweeted. "Adam leaves closed committee hearings to illegally leak confidential information. Must be stopped!"
Within minutes, Schiff fired back, tweeting: "Mr. President, I see you’ve had a busy morning of 'Executive Time.' Instead of tweeting false smears, the American people would appreciate it if you turned off the TV and helped solve the funding crisis, protected Dreamers or...really anything else."
Trump's tweet came shortly before Committee Chairman Devin Nunes, R-Calif., told "Fox & Friends" that there have been "almost 100 leaks" by Democrats on the House Intelligence Committee related to the Russia investigation.
Trump's tweet also reflected frustration with a host of figures, including Schiff's Senate counterpart – Sen. Mark Warner, D-Va., who sits as ranking member on the Senate Intelligence Committee, which conducted its own Russia probe. He also named former FBI Director James Comey, former CIA Director John Brennan, and former Director of National Intelligence James Clapper.
When the Democratic rebuttal memo was released on Feb. 24, Trump, once again, took to Twitter to criticize the document.
"The Democrat memo response on government surveillance abuses is a total political and legal BUST," Trump wrote. "Just confirms all of the terrible things that were done. SO ILLEGAL!"
Schiff countered by saying it confirmed that intelligence officials acted appropriately.
"Wrong again, Mr. President. It confirms the FBI acted appropriately and that Russian agents approached two of your advisors, and informed your campaign that Russia was prepared to help you by disseminating stolen Clinton emails," he replied.
Fox News' Brooke Singman and The Associated Press contributed to this report.