Robert Anderson, a former senior FBI official, testifies before the House Intelligence Committee. (Manuel Balce Ceneta/AP)

Two former FBI spy-hunters warned lawmakers Wednesday that Russian intelligence agencies will keep trying to interfere in U.S. politics, arguing the report by special counsel Robert S. Mueller III shows how pervasive such efforts are.

Robert Anderson and Stephanie Douglas, two former senior FBI officials who specialized in espionage cases, testified before the House Intelligence Committee, which is conducting a separate probe into Russia’s interference in the 2016 election.

The committee’s chairman, Rep. Adam B. Schiff (D-Calif.), has been one of President Trump’s most outspoken critics on matters related to the Russia investigation, and Trump has repeatedly attacked him and called him names.

The hearing was part of a broader effort by congressional Democrats to keep Mueller’s report in the news, but lawmakers divided sharply along political lines about its findings.

Anderson and Douglas left the FBI well before it launched the investigation into Russia’s actions — the case that was taken over by Mueller in May 2017 — but lawmakers consider their experience to be relevant.

Stephanie Douglas, a former senior FBI official, speaks with members of the House Intelligence Committee. (Manuel Balce Ceneta/AP)

Anderson warned that Russian intelligence agencies were engaged in such election interference work well before 2016, and will not stop.

“They’re not leaving. I can guarantee you they’re still here looking at the next presidential election and figuring out how they can still attack it,” Anderson said.

Russia’s outreach to Trump campaign officials in 2016 worked in part, Anderson said, because those around then-candidate Trump “were not savvy at all” in counterintelligence issues.

Douglas said the Mueller report shows how multifaceted Russia’s interference efforts are — targeting multiple individuals connected to campaigns, seeking to establish back channels that could be exploited later.

“They’re looking for opportunities and they’re looking to establish relationships,” she said.

Earlier in her FBI career, Douglas helped convict Harold Nicholson, a CIA official who sold Russian intelligence officials sensitive information about CIA personnel. Nicholson is the rare spy who was caught twice — in 2008, he was charged with conspiring from his prison cell to recruit his son to act as a go-between to sell more secrets to Russia.

Committee Republicans invited a third witness, Andrew McCarthy, a former federal prosecutor who has been critical at times of Mueller’s approach to the Russia investigation.

McCarthy voiced skepticism about how the FBI viewed information from a former British intelligence officer, Christopher Steele, who compiled a dossier of allegations about Trump during the 2016 campaign.

“The criminal process has a way of keeping people honest that the counterintelligence process doesn’t,” McCarthy said.

Rep. Brad Wenstrup (R-Ohio) said the political debate over Russian interference is itself a victory for Russia. Two years earlier, he said, members of the committee were “very nonpartisan. . . . What’s going on right now is we’re giving Mr. Putin everything he wants.”

Since Mueller’s report was released in April, Democrats have struggled to get key witnesses to appear for televised congressional hearings focused on the president’s conduct.

Mueller has proclaimed his strong desire not to testify. Former aides to Trump have been instructed not to do so, and House Democrats are preparing for potential court battles over subpoenas.

Earlier this week, Democrats held a hearing featuring a star witness from the Watergate era — former Nixon White House counsel John W. Dean III. Four decades ago, Dean’s testimony was riveting and crucial to the congressional debate about President Richard M. Nixon’s actions; his appearance Monday, though, underscored the Democrats’ difficulty in finding a compelling witness against the current president.