Russian President Vladimir Putin | Pascal Le Segretain/Getty Images US midterm elections are in Putin’s crosshairs, ex-spy chief says James Clapper believes the Kremlin’s effort is active and even more complex than the 2016 meddling campaign.

Not content with installing Donald Trump in the White House in 2016, Russian President Vladimir Putin is now revising his sophisticated meddling operation in order to outflank U.S. security agencies and tip the scales in the upcoming congressional midterm races, former Director of National Intelligence James Clapper told POLITICO on Wednesday.

Clapper made that assertion as part of a wide-ranging interview timed with the release of his memoirs about his 50-plus years in the U.S. intelligence community, “Facts and Fears: Hard Truths From a Life in Intelligence.”

Clapper, 77, says he thinks the Kremlin, led personally by Putin, is already engaged in an ongoing and active influence effort that is even more elaborate than the one he believes was used during the 2016 campaign to swing the election. That’s based on his years of government service at the highest echelons of the security apparatus, he said in the interview, as well as information he has learned since leaving office Jan. 20, 2017, the day Trump was sworn in as president.

“I have no doubt that they are doing that now, and I think they’re going to do it in ways that are more subtle and harder to detect,” Clapper said of the Russian meddling effort. “I’m sure they went to school to critique what they did in the presidential election in 2016. I think they will find more ways to be subtle, and be a lot less noisy than they were the last time.”

This time, he added, “I think some of the competition among the intelligence services will be moderated.” For Russia, that would be a big improvement over 2016, when its various security agencies — and hacker groups known by nicknames such as Fancy Bear and Cozy Bear — were deployed.

In the book, the veteran spook — and son of an intelligence officer — provides previously undisclosed details about his lead role in the frenzied U.S. effort to stop the Kremlin influence campaign from changing the outcome of the presidential race. Administration officials also had to do that, he said, without creating concerns that President Barack Obama was trying to help the Democratic nominee, former Secretary of State Hillary Clinton.

Clapper, who has served under every president since John F. Kennedy, has often criticized Putin and Trump for what he says are their mutually beneficial roles in the 2016 meddling effort. Since leaving office, he has also been an outspoken critic of Trump for his attacks on the U.S. law enforcement and intelligence agencies investigating the interference campaign.

Clapper further elaborates on those criticisms in the book, contending that Trump has tarnished the office of the presidency and threatened fundamental democratic institutions by claiming that he is the victim of a politically motivated witch hunt. He also notes that while in office, he could not go beyond the joint assessment he issued with Homeland Security Secretary Jeh Johnson in October 2016. That report concluded that the intelligence community was “confident” of the Russian government’s interference in the election, but it did not have the mandate to weigh in on whether the Kremlin effort impacted the outcome of the election.

But Clapper goes much further in his interview, and in the book, by describing how successful he believes the Russian campaign was in putting Trump over the top in a closely fought race that virtually every expert said he was going to lose.

“What I’m offering is what I would call informed opinion, because I didn’t do empirical research on voter decisions, either,” Clapper told POLITICO. “But when I looked at the evidence, the massive effort the Russians made and the multidimensional aspects of it — the number of people that the Russians reached, in many cases who were unknowing, and the fact that the election turned on less than 80,000 votes in three states — it just stretches logic and credulity to think that it didn't have impact.”

“I feel, and this is just my opinion,” he said, “that they swung the election.”

Notoriously averse to media interviews, Clapper made that point even more bluntly in the book, which was released Tuesday evening. “Of course the Russian efforts affected the outcome,” he wrote. “Surprising even themselves, they swung the election to a Trump win.”

Clapper stops short of saying there was active collusion between Trump campaign operatives, and Trump himself, and Russian agents and their proxies. But Trump’s refusal to even acknowledge — and address — the issue, is of grave concern, he said, as is his support for positions friendly to Russia.

“Allegations of collusion and the results of the election,” he writes, “were secondary to the profound threat Russia posed — and poses — to our system.”

Now, as the U.S. government mounts what many critics say is an inadequate response to future Russian meddling efforts, Putin is overseeing an intensive effort to do it again, Clapper told POLITICO.

One of his most serious concerns, Clapper said, is that Russian cyberspooks could use a wealth of knowledge gained from their intrusions of state electoral systems in the 2016 campaign to affect the actual vote this time around. There is no indication that Moscow deleted, manipulated or outright stole state voter data, he said, and “as best we can tell, there was no interference with voter tallies.”

“That’s not to say that they won’t resort to that in the future,” he said. “I don’t think they reconnoitered our voting systems for nothing.”

“In those cases where they reconnoitered voter registration rolls,” Clapper added, “my assumption was that they were just trying to get smart so that if they do it again, they will be a lot more subtle about it.”